A Low Molecular Weight Alanine Aminopeptidase in Urine

Abstract

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.

Isolation and Characterization of Rat Kidney Alanine Aminopeptidase

“…Human AAP is a glycoprotein with a mo lecular weight of about 240,000 daltons in its native form, whereas the soluble form in the urine has a molecular weight of about 160,000 daltons [13,14]. This enzyme is also a zinc metalloprotein [3,4].…”