Use of beta-maltosides (p-nitrophenyl-beta-D-maltoside, 2-chloro-4- nitrophenyl-beta-D-maltoside and 4-methylumbelliferyl-beta-D-maltoside) as substrates for the assay of neutral alpha-glucosidase from human kidney and urine.

The method of assay of neutral alpha-glucosidase from human kidney and urine using beta-maltosides (p-nitrophenyl-beta-D-maltoside [NP-beta-D-maltoside], 2-chloro-4-nitrophenyl-beta-D-maltoside]) [CNP-beta-D-maltoside] and 4-methylumbelliferyl-beta-D-maltosides ([MU-beta-D-maltoside]) as substrates and beta-glucosidase as an auxiliary enzyme is proposed. All three beta-maltosides are suitable substrates for the determination of neutral alpha-glucosidase activity but MU-beta-D-maltoside is the most sensitive due to its methylumbelliferyl moiety. The method is simple, convenient and 10-fold more sensitive than the commonly used alpha-glucosidase assay procedure with the corresponding synthetic alpha-glucosides, p-nitrophenyl- alpha-D-glucoside (NP-alpha-D-glucoside) and 4-methylumbelliferyl-alpha-D-glucoside (MU-alpha-D-glucoside). A modification of the method, with p-nitrophenyl-beta-D-maltoside as substrate, was applied to the semiautomatic assay of urinary alpha-glucosidase in 96-well microtitre plates.