title: A continuous method for the determination of leucine aminopeptidase in human serum with L-leucinamide as substrate.
abstract: A continuous procedure for the determination of leucine aminopeptidase is described. L-leucinamide is used as substrate and the liberated ammonia is determined with the glutamate dehydrogenase reaction. The enzyme is Mn2+-activated and 30 mumol/l MnCl2 is necessary for an optimal activity measurement. Influence of buffer type, buffer concentration and pH are reported together with the apparent Km values of leucine aminopeptidase for L-leucinamide and of glutamate dehydrogenase for 2-oxoglutarate. Amastatin, a potent inhibitor, inhibits the reaction of leucine aminopeptidase completely, whereas it has no inhibitory effect on the reaction with glutamate dehydrogenase. The normal reference interval for leucine aminopeptidase is 12-65 U/l at 37 degrees C. The properties of the enzyme are discussed.
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000900:Anti-Bacterial Agents; D005969:Glutamate Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007501:Iron / Q000494:pharmacology; D007700:Kinetics; D007930:Leucine / Q000031:analogs & derivatives* / Q000378:metabolism; D007931:Leucyl Aminopeptidase / Q000037:antagonists & inhibitors / Q000097:blood*; D008345:Manganese / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D010455:Peptides; D013379:Substrate Specificity; D015032:Zinc / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D009842:Oligopeptides; D010455:Peptides; D008345:Manganese; D009249:NADP; D000244:Adenosine Diphosphate; C016977:amastatin; D007501:Iron; D005969:Glutamate Dehydrogenase; D007931:Leucyl Aminopeptidase; D007930:Leucine; D015032:Zinc; C013086:leucinamide