Benders'dictionary of nutrition and food technology

216An alternative to part of glycolysis, the pentose phosphatepathway or hexose monophosphate shunt, is important in theformation of reduced NADPH for fatty acid synthesis.glucose oxidase Enzyme (EC 1.1.3.4) that oxidises glucose to gluconicacid, with the formation of hydrogen peroxide. Used forspecific quantitative determination of glucose, including urineand blood glucose, and to remove traces of glucose from foodstuffs(e.g. from dried egg to prevent the maillard reactionduring storage). Also used to remove traces of oxygen fromproducts such as beer, wine, fruit juices and mayonnaise toprevent oxidative rancidity. Originally isolated from Penicilliumnotatum and called notatin; main commercial source isAspergillus niger.glucose6-phosphate dehydrogenase deficiency See favism.glucose syrups See syrup; dextrose equivalent value.glucose tolerance The ability of the body to deal with a relativelylarge dose of glucose is used as a test for diabetes mellitus. Thefasting subject ingests 50 or 75g of glucose (sometimes calculatedas 1 g/kg body weight) and the concentration of blood glucose ismeasured at intervals. In normal subjects the fasting glucose concentrationis between 4.5 and 5.5 mmol/L, and rises to about7.5 mmol/L, returning to the starting level within 1–1 1 / 2 h. In diabetes,it rises considerably higher and takes longer to return tothe baseline value. The graph of the results forms a glucosetolerance curve.glucose tolerance factor (GTF) Organic chelate of chromium, M raround 1500, variously reported to contain nicotinic acid (seeniacin), glutathione and other amino acid derivatives. Potentiatesthe action of insulin, but has no activity in the absence ofinsulin. Acts by increasing the protein kinase activity of theinsulin receptor when insulin is bound.glucosides See glycosides.glucosinolates Substances occurring widely in Brassica spp.(e.g. Brussels sprouts, cabbage, watercress, radishes); brokendown by the enzyme myrosinase (thioglucosidase, EC 3.2.3.1) toyield, among other products, the mustard oils which are responsiblefor the pungent flavour (especially in mustard andhorseradish).Several of the glucosinolates that are thioesters interfere withthe metabolism of iodine by the thyroid gland (see thyroid hormones),and hence are goitrogens. There is evidence that thevarious glucosinolates in vegetables may have useful anticanceractivity, since they increase the rate at which a variety of potentiallytoxic and carcinogenic compounds are conjugated andexcreted (phase ii metabolism).