Pentosuria, a component of
Garrod’s tetrad, is a condition where the sugar L-
xylulose
Xylulose is a ketopentose, a monosaccharide containing five carbon atoms, and including a ketone functional group. It has the chemical formula . In nature, it occurs in both the L- and D-enantiomers. 1-Deoxyxylulose is a precursor to terpenes via ...
, a
pentose
In chemistry, a pentose is a monosaccharide (simple sugar) with five carbon atoms. The chemical formula of many pentoses is , and their molecular weight is 150.13 g/mol.[urine
Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...]
in unusually high concentrations. It was characterized as
an inborn error of carbohydrate metabolism in 1908.
It is associated with a deficiency of
L-xylulose reductase, necessary for xylitol metabolism.
L-
Xylulose
Xylulose is a ketopentose, a monosaccharide containing five carbon atoms, and including a ketone functional group. It has the chemical formula . In nature, it occurs in both the L- and D-enantiomers. 1-Deoxyxylulose is a precursor to terpenes via ...
is a
reducing sugar
A reducing sugar is any sugar that is capable of acting as a reducing agent. In an alkaline solution, a reducing sugar forms some aldehyde or ketone, which allows it to act as a reducing agent, for example in Benedict's reagent. In such a react ...
, so it may give false diagnosis of diabetes, as it is found in high concentrations in urine. However glucose metabolism is normal in people with pentosuria, and they are not
diabetic
Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of th ...
.
Patients of pentosuria have a low concentration of the sugar d-xyloketose. Using phenyl pentosazone crystals, phloroglucin reaction, and absorption spectrum, pentose can be traced back as the reducing substance in urine, with those that have pentosuria.
Research has shown that pentosuria appears in 3 forms. The most widely studied is essential pentosuria, where a couple of grams of L-xylulose are released into a person's system daily.
, contained in red blood cells, is composed of both a major and minor
isozyme
In biochemistry, isozymes (also known as isoenzymes or more generally as multiple forms of enzymes) are enzymes that differ in amino acid sequence but catalyze the same chemical reaction. Isozymes usually have different kinetic parameters (e.g. di ...
.
For those diagnosed with essential pentosuria, the major isozyme appears to be the same as the minor one.
Alimentary pentosuria can be acquired through fruits high in pentose.
Finally, drug-induced pentosuria can be developed by those exposed to morphine, fevers, allergies, and some hormones.
Those diagnosed with Pentosuria are predominantly of Jewish heritage.
It is a harmless defect, and no cure is needed.
References
External links
Urine
{{endocrine-disease-stub
Inborn errors of carbohydrate metabolism