ArsB And ArsAB Family
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Arylsulfatase B (N-acetylgalactosamine-4-sulfatase, chondroitinsulfatase, chondroitinase, acetylgalactosamine 4-sulfatase, N-acetylgalactosamine 4-sulfate sulfohydrolase, ) is an
enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
associated with mucopolysaccharidosis VI (Maroteaux–Lamy syndrome). Arylsulfatase B is among a group of arylsulfatase enzymes present in the lysosomes of the
liver The liver is a major metabolic organ (anatomy), organ exclusively found in vertebrates, which performs many essential biological Function (biology), functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of var ...
,
pancreas The pancreas (plural pancreases, or pancreata) is an Organ (anatomy), organ of the Digestion, digestive system and endocrine system of vertebrates. In humans, it is located in the abdominal cavity, abdomen behind the stomach and functions as a ...
, and
kidney In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...
s of animals. The purpose of the enzyme is to hydrolyze sulfates in the body. ARSB does this by breaking down
glycosaminoglycan Glycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case o ...
s (GAGs), which are large sugar molecules in the body. ARSB targets two GAGs in particular:
dermatan sulfate Dermatan sulfate is a glycosaminoglycan (formerly called a mucopolysaccharide) found mostly in skin, but also in blood vessels, heart valves, tendons, and lungs. It is also referred to as chondroitin sulfate B, although it is no longer classifi ...
and
chondroitin sulfate Chondroitin sulfate is a sulfated glycosaminoglycan (GAG) composed of a chain of alternating sugars (N-Acetylgalactosamine, N-acetylgalactosamine and glucuronic acid). It is usually found attached to proteins as part of a proteoglycan. A chondroit ...
.U.S. National Library of Medicine
"ARSB"
Genetics Home Resource, 7 November 2010, Retrieved 22 November 2010
Over 130 mutations to ARSB have been found, each leading to a deficiency in the body. In most cases, the mutation occurs on a single
nucleotide Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...
in the sequence. An arylsulfatase B deficiency can lead to an accumulation of GAGs in lysosomes, which in turn can lead to mucopolysaccharidosis VI. Used as a pharmaceutical drug, the enzyme is known under the International Nonproprietary Name galsulfase and is sold under the brand name Naglazyme. Galsulfase was approved for medical use in the United States in May 2005 and in European Union in January 2006. Galsulfase is indicated for long-term enzyme-replacement therapy in people with a confirmed diagnosis of mucopolysaccharidosis VI (MPS VI; N-acetylgalactosamine-4-sulfatase deficiency; Maroteaux-Lamy syndrome).


Structure

The primary structure of ''
Escherichia coli ''Escherichia coli'' ( )Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Escherichia'' that is commonly fo ...
'' arylsulfatase B contains a primary sequence of 502 amino acids. Its secondary structure is quite complex, containing numerous
alpha helices An alpha helix (or α-helix) is a sequence of amino acids in a protein that are twisted into a coil (a helix). The alpha helix is the most common structural arrangement in the secondary structure of proteins. It is also the most extreme type of l ...
(20 total containing 138 residues) and
beta sheet The beta sheet (β-sheet, also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a gene ...
s (21 strands total containing 87 residues). The functional enzyme is believed to be a homo
tetramer A tetramer () (''tetra-'', "four" + '' -mer'', "parts") is an oligomer formed from four monomers or subunits. The associated property is called ''tetramery''. An example from inorganic chemistry is titanium methoxide with the empirical formula ...
. Due to the complexity of arylsulfatase B's secondary structure, many hydrophobic and hydrophilic regions are present, as demonstrated by the Kyte-Doolittle hydropathy plot:


Medical uses

Galsulfase is used to treat adults and children who have mucopolysaccharidosis VI (MPS VI or Maroteaux-Lamy syndrome). This disease is caused by the lack of an enzyme called N-acetylgalactosamine 4-sulfatase, which is needed to break down substances in the body called glycosaminoglycans (GAGs). If the enzyme is not present, GAGs cannot be broken down and they build up in the cells. This causes the signs of the disease, the most noticeable being a short body, a large head and difficulty moving about. The disease is usually diagnosed in infants between one and five years of age. Galsulfase has been shown to improve walking and stair-climbing capacity. The most common adverse reactions (≥10%) are: rash, pain, urticaria, pyrexia, pruritus, chills, headache, nausea, vomiting, abdominal pain and dyspnea. The most common adverse reactions requiring interventions are infusion-related reactions. Galsulfase (N-acetylgalactosamine-4-sulfatase, recombinant human) was granted orphan drug designation by both the European Commission and the U.S.
Food and Drug Administration The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respo ...
(FDA).


Role in cystic fibrosis

Expression and activity of ARSB were found to be related to the function of
cystic fibrosis transmembrane conductance regulator Cystic fibrosis transmembrane conductance regulator (CFTR) is a membrane protein and anion channel in vertebrates that is encoded by the ''CFTR'' gene. Geneticist Lap-Chee Tsui and his team identified the ''CFTR'' gene in 1989 as the gene lin ...
(CFTR), the membrane channel deficient in
cystic fibrosis Cystic fibrosis (CF) is a genetic disorder inherited in an autosomal recessive manner that impairs the normal clearance of Sputum, mucus from the lungs, which facilitates the colonization and infection of the lungs by bacteria, notably ''Staphy ...
. Measurements in cystic fibrosis cell line IB3 and its derivative cell line C38, which has a functional CFTR, showed increased ARSB activity and expression in the C38 line. CFTR potentiator VRT-532 increased ARSB expression and activity in cystic fibrosis cells to the level in the normal bronchial epithelial cells.


Role in malignancy

ARSB has been studied in a variety of cancers. Cultured normal mammary epithelial and
myoepithelial cells Myoepithelial cells (sometimes referred to as myoepithelium) are cells usually found in glandular epithelium as a thin layer above the basement membrane but generally beneath the lumen (anatomy), luminal cells. These may be positive for ACTA2, alph ...
had significantly higher ARSB activity than cultured malignant mammary cells. Immunohistochemistry in the colon showed decreased membrane ARSB staining in
colon cancer Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel ...
compared to normal colon, as well as in higher grade malignancies. ARSB activity was lower in malignant than normal prostate tissue, and immunostaining of prostate tissue microarrays showed not only decreasing ARSB staining in
prostate cancer Prostate cancer is the neoplasm, uncontrolled growth of cells in the prostate, a gland in the male reproductive system below the bladder. Abnormal growth of the prostate tissue is usually detected through Screening (medicine), screening tests, ...
tissue of a higher Gleason score, but also lower staining in patients with recurrent compared to non-recurrent cancer. ARSB staining was a greater predictor of recurrence than Prostate-specific antigen (PSA) test, indicating possible future role of ARSB as a prognostic biomarker of prostate cancer. Further evidence of ARSB as a tumor suppressor was determined by molecular studies in cell cultures where ARSB was silenced by
siRNA Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded non-coding RNA molecules, typically 20–24 base pairs in length, similar to microRNA (miRNA), and operating within the RN ...
. The studies showed that decrease of ARSB leads to increase in free
galectin-3 Galectin-3 is a protein that in humans is encoded by the ''LGALS3'' gene. Galectin-3 is a member of the lectin family, of which 14 mammalian galectins have been identified. Galectin-3 is approximately 30 kDa and, like all galectins, contains a ...
, which attaches more strongly to less sulfated chondroitin 4-sulfate. Galectin-3 then acts on transcription factors AP-1 to increase expression of chondroitin sulfate
proteoglycan Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a serine (Ser) residue to w ...
versican Versican is a large extracellular matrix proteoglycan that is present in a variety of human tissues. It is encoded by the ''VCAN'' gene. Versican is a large chondroitin sulfate proteoglycan with an apparent molecular mass of more than 1000kDa. I ...
and SP-1 to increase expression of WNT9A. Another mechanism by which reduced ARSB is associated with carcinogenesis is through increased binding of
SHP2 Tyrosine-protein phosphatase non-receptor type 11 (PTPN11) also known as protein-tyrosine phosphatase 1D (PTP-1D), Src homology region 2 domain-containing phosphatase-2 (SHP-2), or protein-tyrosine phosphatase 2C (PTP-2C) is an enzyme that in hu ...
to more sulfated chondroitin 4-sulfate, which leads to increased phosphorylation of p38 and
MITF Microphthalmia-associated transcription factor also known as class E basic helix-loop-helix protein 32 or bHLHe32 is a protein that in humans is encoded by the ''MITF'' gene. MITF is a basic helix-loop-helix leucine zipper transcription factor ...
with subsequently increased expression of
GPNMB Transmembrane glycoprotein NMB is a protein that in humans is encoded by the ''GPNMB'' gene. Two transcript variants encoding 560 and 572 amino acid isoforms have been characterized for this gene in humans. The mouse and rat orthologues of GPNMB ...
.


Role in metabolism

Reduced sulfate availability due to impaired activity of ARSB has been linked to increased
aerobic Aerobic means "requiring air," in which "air" usually means oxygen. Aerobic may also refer to * Aerobic exercise, prolonged exercise of moderate intensity * Aerobics, a form of aerobic exercise * Aerobic respiration, the aerobic process of cellu ...
glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvic acid, pyruvate and, in most organisms, occurs in the liquid part of cells (the cytosol). The Thermodynamic free energy, free energy released in this process is used to form ...
, as shown by an increase in
NADH Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an ade ...
and
NADPH Nicotinamide adenine dinucleotide phosphate, abbreviated NADP or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require N ...
, reduced oxygen consumption, increased extracellular acidification and
serum Serum may refer to: Biology and pharmacology *Serum (blood), plasma from which the clotting proteins have been removed **Antiserum, blood serum with specific antibodies for passive immunity *Serous fluid, any clear bodily fluid Places *Serum, Ind ...
lactate, and a decline in
mitochondrial A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is used ...
membrane potential Membrane potential (also transmembrane potential or membrane voltage) is the difference in electric potential between the interior and the exterior of a biological cell. It equals the interior potential minus the exterior potential. This is th ...
in ARSB-silenced cells and ARSB-
null mouse A knockout mouse, or knock-out mouse, is a genetically modified mouse (''Mus musculus'') in which researchers have inactivated, or "knocked out", an existing gene by replacing it or disrupting it with an artificial piece of DNA. They are important ...
tissues.


Extra-lysosomal localization

Although primarily a lysosomal enzyme, ARSB was also found to localize at the cell membrane of
hepatocytes A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in: * Protein synthesis * Protein storage * Transformation of carbohydrates * Synthesis of cholesterol, bile ...
,
sinusoidal endothelial cells A liver sinusoid is a type of capillary known as a sinusoidal capillary, discontinuous capillary or sinusoid, that is similar to a fenestrated capillary, having discontinuous endothelium that serves as a location for mixing of the oxygen-rich blo ...
, and
Kupffer cells Kupffer cells, also known as stellate macrophages and Kupffer–Browicz cells, are specialized cells localized in the liver within the lumen of the liver sinusoids and are adhesive to their endothelial cells which make up the blood vessel walls. K ...
in the liver, as well as in the apical membranes of normal and malignant colonic and prostatic
epithelial cells Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...
, by
immunohistochemistry Immunohistochemistry is a form of immunostaining. It involves the process of selectively identifying antigens in cells and tissue, by exploiting the principle of Antibody, antibodies binding specifically to antigens in biological tissues. Alber ...
and
immunofluorescence Immunofluorescence (IF) is a light microscopy-based technique that allows detection and localization of a wide variety of target biomolecules within a cell or tissue at a quantitative level. The technique utilizes the binding specificity of anti ...
studies. Membrane immunostaining in the colon and prostate was lower in malignant than in normal tissue and also was lower in higher grade malignancies. ARSB activity assay in the membrane and cytosol fractions of cultured bronchial epithelial cells showed that the activity was several-fold greater in the membrane fraction.


See also

*
Aryl In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl. "Aryl" is used for the sake of abbreviation or generalization, and "Ar" is used ...
*
Sulfatase In biochemistry, sulfatases are a class of enzymes of the esterase class that catalyze the hydrolysis of sulfate esters into an Alcohol (chemistry), alcohol and a bisulfate: :\ce \quad \xrightarrow
text Text may refer to: Written word * Text (literary theory) In literary theory, a text is any object that can be "read", whether this object is a work of literature, a street sign, an arrangement of buildings on a city block, or styles of clothi ...
\quad \ce These may be found on a rang ...


References


Further reading

* * *


External links


Medical Dictionary
Arylsulfatase B function.
Protein Data Base (PDB)
Arylsulfatase structure.
Genetics Home Reference
Arylsulfatase B function. * * * {{Portal bar , Medicine Orphan drugs