Characterization of particulate and soluble variants of the brush-border enzymes alanine aminopeptidase, alkaline phosphatase and gamma-glutamyltransferase in human urine.

The urinary brush-border enzymes alanine aminopeptidase, alkaline phosphatase and gamma-glutamyltransferase can be separated by ultracentrifugation into a particulate and a soluble fraction. These variants have been characterized with respect to their kinetic data, heat stability, electrophoretic mobility and behaviour in gel chromatography and affinity chromatography. Both variants of these enzymes show nearly identical Km values and activity curves as functions of rho H and substrate concentration. The particulate variant is more heat-sensitive than the soluble one. The soluble variant as well as the particulate form consist of one fraction bound by Con A-sepharose and another one unbound by it. Origins and nature of these multiple variants in connection with their possible diagnostic significance are discussed.