Methods for Measuring Urinary Enzyme Activities

摘要: Aminopeptidases (α-aminoacylpeptide hydrolases, EC 3.4.11) comprise a group of exopeptidases, which split single amino acids from the N-terminus peptide chains. Two, namely cytosolic (EC 3.4.11.1) and microsomal forms 3.4.11.2), are relatively broad substrate specificity. The enzyme, “classic” leucine aminopeptidase [6], hydrolyzes L-peptides with an N-terminal residue. recommended substrates L-leucinamide [4, 5] L-leucine hydrazide [7]. Chromogenic like L-leucine-4-nitroanilide or L-leucine-β-naphthylamide not hydrolyzed. pH optimum enzyme is between 9–10; it activated by Mg2+ Mn2+ ions inhibited Co2+ [19]. concerns us here, acts preferentially on peptides alanine, name alanine (AAP) was introduced [18]; L-alanine-β-naphthylamide [17] L-alanine-4-nitroanilide [21] substrates. L-Leucine derivatives [3] [20] also split, although at slower rate. then, termed either AAP (LAP), depending being used. terminology becomes confusing, particularly when one considers that, strictly speaking, “leucine aminopeptidase” should be reserved for enzyme. L-Alanine-4-nitroanilide choice determination because its relative specificity (L-leucine-4-nitroanilide cystyl aminopeptidases), higher hydrolysis rate better solubility as compared L-leucine-4-nitroanilide. main advantages nitroanilides over naphthylamides possibility continuous recording release 4-nitroaniline easy adaptation assay to automated analysers.