title: Substrate specificity of alkaline phosphatase from human polymorphonuclear leukocytes.
abstract: The ability of alkaline phosphatase in purified preparations from human neutrophils and liver to utilize ATP or inorganic pyrophosphate as substrate depended upon the Mg2+ concentration. With pyrophosphate present (1.0 mmol/l), activity peaked at Mg2+ concentrations of 0.25 to 0.50 mmol/l and fell sharply above this. By contrast, p-nitrophenylphosphatase activity was activated with Mg2+ concentration up to 0.75 mmol/l but above this was constant to 5.0 mmol/l. Hydrolysis was abolished by L-levamisole, a specific inhibitor of alkaline phosphatase. Testing butanol extracts of neutrophils from 50 healthy subjects showed good correlation of enzyme activity with p-nitrophenylphosphate and ADP (r = 0.90), and between p-nitrophenylphosphate and pyridoxal phosphate (r = 0.96) as substrate, consistent with hydrolysis of all three phosphoesters by one enzyme. Inhibition studies yielded no evidence of a specific pyridoxal phosphatase. Alkaline phosphatase from human neutrophils has the same broad substrate specificity as other molecular forms of the human enzyme and, like other forms, has little or no activity towards phosphoesters complexed with Mg2+.
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000097:blood*; D006801:Humans; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009504:Neutrophils / Q000201:enzymology*; D009596:Nitrophenols / Q000378:metabolism; D009943:Organophosphorus Compounds / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D009596:Nitrophenols; D009943:Organophosphorus Compounds; C008644:nitrophenylphosphate; D000244:Adenosine Diphosphate; D000469:Alkaline Phosphatase; D008274:Magnesium