Intrinsic properties of FAD-linked glycerophosphate dehydrogenase in islets from normal and streptozotocin-induced diabetic rats.
An acquired or inherited deficiency of FAD-linked glycerophosphate dehydrogenase activity in the pancreatic islet B-cell was recently proposed to represent a far-from-uncommon contributing factor in the pathogenesis of non-insulin-dependent diabetes mellitus. In the present study, it was investigated whether the postulated genomic defect coincides with the biosynthesis of an enzymic protein with altered catalytic properties and might concern an isoenzyme distinct from that found in extrapancreatic tissues. The activity of FAD-linked glycerophosphate dehydrogenase, as measured by either a radioisotopic or colorimetric procedure, was indeed severely decreased in islets from rats injected with streptozotocin. The intrinsic properties of the enzyme were preserved, however, as judged from the affinity for L-glycerol-3-phosphate, the ratio in reaction velocity using either FAD or iodonitrotetrazolium as electron acceptor and the activation of the enzyme by Ca2+. When the same kinetic parameters were compared in islet, liver and spleen homogenates from normal rats, significant differences were observed, however, between these three tissues, suggesting the possible existence of distinct isoenzymes.
Laboratory of Experimental Medicine, Brussels Free University, Belgium.
J
J
Rasschaert
W J
WJ
Malaisse
D000818:Animals; D003124:Colorimetry / Q000379:methods; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D005260:Female; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism*; D007515:Islets of Langerhans / Q000201:enzymology*; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D011865:Radioisotope Dilution Technique; D051381:Rats; D012016:Reference Values; D013154:Spleen / Q000201:enzymology; D014316:Tritium
D014316:Tritium; D005182:Flavin-Adenine Dinucleotide; D005993:Glycerolphosphate Dehydrogenase