A new micro-assay for human liver alanine: glyoxylate aminotransferase

A micro radiochemical method has been developed for the assay of the human liver peroxisomal enzyme alanine: glyoxylate aminotransferase (EC 2.6.1.44). The method, based on the electrophoretic separation of [14C]alanine (substrate) from [14C]pyruvate (product) is at least fifty times more sensitive than the currently-used spectrophotometric double enzyme method (Rowsell et al, Int J Biochem 1972;3: 247-257), enabling the enzymatic diagnosis of primary hyperoxaluria type 1 to be carried out on only 100 micrograms of human liver tissue obtained by percutaneous needle biopsy. The increased sensitivity of the new method allows the assay conditions to be such that they are on the linear parts of the time-course and protein concentration curves. This results in the activities of alanine: glyoxylate aminotransferase in human liver samples being 20-50% higher than those determined by the spectrophotometric method.