title: Essential tyrosyl residues of human placental alkaline phosphatase.
abstract: Human placental alkaline phosphatase was inactivated with tetranitromethane in a biphasic process. Spectral and amino acid analysis demonstrated that the inactivation was due to the conversion of tyrosine residues to 3-nitrotyrosine. The inactivation process showed saturation kinetics. Protection of the enzyme against tetranitromethane inactivation was afforded by inorganic phosphate. The binding affinity between the modified enzyme and inorganic phosphate was decreased. Our results suggest the involvement of tyrosyl residues in the locus of phosphoryl site of the phosphorylated enzyme forms.
mesh_terms: D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors*; D005260:Female; D006801:Humans; D007700:Kinetics; D008697:Methane / Q000031:analogs & derivatives*; D010710:Phosphates / Q000494:pharmacology; D010920:Placenta / Q000201:enzymology*; D011247:Pregnancy; D011485:Protein Binding; D013053:Spectrophotometry; D013774:Tetranitromethane / Q000494:pharmacology*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000032:analysis*
chemical_list: D010710:Phosphates; C002744:3-nitrotyrosine; D014443:Tyrosine; D000469:Alkaline Phosphatase; D013774:Tetranitromethane; D008697:Methane