Lipstatin is a potent, irreversible

inhibitor Inhibitor or inhibition may refer to: Biology * Enzyme inhibitor, a substance that binds to an enzyme and decreases the enzyme's activity * Reuptake inhibitor, a substance that increases neurotransmission by blocking the reuptake of a neurotransmi ...

pancreatic lipase Pancreatic lipases () are a protein family, family of lipolytic enzymes that hydrolyse ester linkages of triglycerides. Lipases are widely distributed in animals, plants and prokaryotes. At least three tissue-specific isozymes exist in higher ...

. It is a

natural product A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical s ...

that was first isolated from the

actinobacterium The Actinomycetota (or Actinobacteria) are a diverse phylum of Gram-positive bacteria with high GC content. They can be terrestrial or aquatic. They are of great importance to land flora because of their contributions to soil systems. In soil t ...

Streptomyces toxytricini ''Streptomyces toxytricini'' is a Gram-positive bacterium belonging to the genus ''Streptomyces''. It produces the pancreatic lipase inhibitor lipstatin, of which the antiobesity drug orlistat Orlistat, sold under the brand name Xenical amon ...

''. The popular antiobesity drug

orlistat Orlistat, sold under the brand name Xenical among others, is a medication used to treat obesity. Its primary function is preventing the absorption of fats from the human diet by acting as a lipase inhibitor, thereby reducing caloric intake. It ...

(trade names Xenical and alli) is a

saturated Saturation, saturated, unsaturation or unsaturated may refer to: Chemistry *Saturated and unsaturated compounds, a classification of compounds related to their ability to resist addition reactions **Degree of unsaturation **Saturated fat or satur ...

derivative of lipstatin.

Biosynthesis

Lipstatin is composed of a 2-hexyl-3,5-dihydroxy-7,10-hexadecadienoic-β-lactone 22 carbon backbone from

fatty acid synthesis In biochemistry, fatty acid synthesis is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes. Two ''De novo synthesis, de novo'' fatty acid syntheses can be distinguished: cytosolic fatty acid synthesis (FAS/FASI) ...

pathway and an ''N''-formyl-

L-leucine Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- ca ...

group ester linked to the 5-hydroxyl group of the back bone. The composts of the lipstatin are ultimately from

linoleic acid Linoleic acid (LA) is an organic compound with the formula . Both alkene groups () are ''cis''. It is a fatty acid sometimes denoted 18:2 (n−6) or 18:2 ''cis''-9,12. A linoleate is a salt or ester of this acid. Linoleic acid is a polyunsat ...

octanoic acid Caprylic acid (), also known under the systematic name octanoic acid or C8 Acid, is a saturated fatty acid, medium-chain fatty acid (MCFA). It has the structural formula , and is a colorless oily liquid that is minimally soluble in water with a ...

, and

. The 22 carbon β-lactone moiety is derived from

Claisen condensation The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base. The reaction produces a β-keto ester or a β- diketone. It is named ...

between 3-hydroxytetradeca-5,8-dienyl-CoA derived from

and hexyl-malonyl-ACP derived from

. Linoleic acid is first attached to CoA through some

acyl-CoA synthetase Acyl-CoA synthetases, also known as acyl-CoA ligases, are enzymes that "activate" fatty acids by thioesterification to coenzyme A. It represents the initial step of fatty acid metabolism so that fatty acids can participate in catabolic and anabolic ...

homologue synthesized by lipstatin biosynthetic operons (''Lst'') and goes through two

β-oxidation In biochemistry and metabolism, beta oxidation (also β-oxidation) is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA. Acetyl-CoA enters ...

to hydroxytetradeca-5,8-dienyl-CoA. 3’ hydroxyl group from solution H₂O is added by enoyl reductase homologue followed by enoyl hydratase homologue. Octanoic acid is also attached to CoA through similar

homologue (''LstC'') to form

octanoyl-CoA Octanoyl-coenzyme A is the endpoint of beta oxidation in peroxisomes. It is produced alongside acetyl-CoA and transferred to the mitochondria to be further oxidized into acetyl-CoA. See also *Caprylic acid Caprylic acid (), also known under ...

. Octanoyl-CoA is 2’ carboxylated and loaded to

acyl carrier protein The acyl carrier protein (ACP) is a cofactor of both fatty acid and polyketide biosynthesis machinery. It is one of the most abundant proteins in cells of ''E. coli.'' In both cases, the growing chain is bound to the ACP via a thioester derived fr ...

(ACP) borrowed from primary metabolism to form hexyl-malonyl-ACP. The β-lactone ring is formed by reduction of 3-

keto group In organic chemistry, a ketone is an organic compound with the structure , where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group (a carbon-oxygen double bond C=O). The simplest ketone is acetone ( ...

by 3-hydroxysteroid

dehydrogenase A dehydrogenase is an enzyme belonging to the group of oxidoreductases that oxidizes a substrate by reducing an electron acceptor, usually NAD+/NADP+ or a flavin coenzyme such as FAD or FMN. Like all catalysts, they catalyze reverse as well as ...

homologue followed by a spontaneously

nucleophilic attack In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they a ...

of the 3-

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

on the carbonyl of the ACP-tether acyl intermediate. This step follows the

esterification In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...

of the ''N''-formyl-L-leucine group. The ''N''-formyl-L-leucine group is derived from

. L-leucine was activated by ''LstE'' forming

thioester In organic chemistry, thioesters are organosulfur compounds with the molecular structure . They are analogous to carboxylate esters () with the sulfur in the thioester replacing oxygen in the carboxylate ester, as implied by the thio- prefix ...

and its α-amine group is

formylated Formylation refers to any chemical processes in which a compound is functionalized with a formyl group (-CH=O). In organic chemistry, the term is most commonly used with regards to aromatic compounds (for example the conversion of benzene to benz ...

by ''LstF''. Finally, 5-hydroxyl of 22 carbon β-lactone backbone nucleophilic attacks on the acyl carbon of the formyl-leucine and forms the lipstatin.

References

{{Reflist Hydrolase inhibitors Lactones Oxetanes Carboxylate esters Formamides Lipase inhibitors