A low molecular weight alanine aminopeptidase in urine. Biochemical equivalent of tubular atrophy?

Using agarose gel electrophoresis, a faster moving alanine aminopeptidase (EC 3.4.11.2) has been demonstrated in the urine from cases of Fanconi syndrome, endemic (Balkan) nephropathy and advanced renal insufficiency. The enzyme was partially purified and its properties (isoelectric point, molecular weight, substrate specificity, influence of metal ions, Michaelis constant, antigenic behavior) were compared with those of normal kidney alanine aminopeptidase. Isoelectric points and antigenic properties are identical, but the molecular weights differ by a factor of about 2. Therefore, the greater electrophoretic mobility is due to the smaller size of the atypical enzyme.