An inhibitory substance of glyceraldehyde 3-phosphate dehydrogenase in urine of diabetic patients.

In urine of diabetics, a significantly great inhibitory activity of glyceraldehyde 3-phosphate dehydrogenase (GAP-Dehyd) was observed compared with that of normal subjects. The 0.2 ml of urine from 41 patients with diabetes mellitus inhibited 0.5 units of GAP-Dehyd by 27.2 +/- 3.0% (mean +/- S.E.M.), while that from 17 normal volunteers inhibited only by 9.0 +/- 1.0% (P less than 0.05). This inhibitory substance was extracted by 90% ethanol from diabetic urine and partially purified by anion exchange chromatography using Dowex-1 (HCOO type). The molecular weight of this substance was confirmed to be 100--300 daltons by an analysis on Biogel P-4 gel filtration chromatography. And analysis by thin layer chromatography using silicagel plate showed that this inhibitor was a ninhydrin reactive substance which has not been reported previously. From the above facts, it was assumed that the inhibitory substance of GAP-Dehyd in urine of diabetics was a new acidic compound of low molecular weight containing an amino residue in the molecule.