Xylose isomerase

Xylose Isomerase (also known as D-xylose ketol-isomerase or glucose isomerase) is an enzyme that catalyzes the isomerization of glucose into fructose. It is a key enzyme in the carbohydrate metabolism pathway and plays a significant role in the industrial production of high fructose corn syrup (HFCS) and biofuel.

Function

Xylose isomerase catalyzes the conversion of D-xylose into D-xylulose and D-glucose into D-fructose. This reaction is reversible and involves the movement of a functional group (the carbonyl group) from one position to another within the same molecule. The enzyme is crucial in the metabolism of pentose sugars in the body and is also used industrially to convert glucose into fructose, which is sweeter and therefore more desirable in many food products.

Structure

Xylose isomerase is a tetramer with four identical subunits. Each subunit contains a magnesium and a cobalt ion, which are essential for its catalytic activity. The enzyme has an open, active site that allows for the binding of the sugar substrate.

Industrial Use

In the food industry, xylose isomerase is used to produce high fructose corn syrup (HFCS), a sweetener used in many processed foods and beverages. The enzyme is also used in the production of biofuels, where it converts xylose, a sugar derived from plant biomass, into xylulose, which can be fermented into ethanol.

Clinical Significance

Deficiency in xylose isomerase can lead to pentosuria, a condition characterized by the excretion of large amounts of pentose sugars in the urine. This condition is generally benign but can be indicative of more serious underlying health issues.