Catabolism of Ap4A and Ap3A in human serum. Identification of isoenzymes and their partial characterization.
A hydrolase splitting adenosine (5')triphospho(5')adenosine (Ap3A) and adenosine(5')tetraphospho(5')adenosine (Ap4A) has recently been highly purified from human plasma [Lüthje, J. and Ogilvie, A. (1985) Eur. J. Biochem. 149, 119-127]. This enzyme has been shown to have 5'-nucleotide phosphodiesterase activity (5'-NPD). Three isoenzymes splitting Ap4A and Ap3A were found in human serum by means of native polyacrylamide gel electrophoresis. They exactly comigrated with the 5'-NPD isoenzymes I, III and IV according to published nomenclature, and were designated Ap4Aase isozymes I, III and IV. Their Km values with Ap4A as a substrate were 3 microM, 2 microM and 10 microM, respectively. No Ap4A splitting activity corresponding to 5'-NDP-II was found. Further experiments were designed to prove the identity of Ap4Aases with 5'-NPD isoenzymes. Corresponding isozymes of both activities showed identical behaviour upon delipidation of serum with n-butanol: activities I and III were inactivated, whereas IV remained unaffected. Addition of phosphate stimulated Ap4Aase and 5'-NPD isoenzymes I and III, whereas both activities of isozyme IV were inhibited. Further evidence for the identity was obtained when investigating a series of normal and pathological sera showing decreased as well as increased activities of the single isoenzymes. In all cases Ap4Aase and 5'-NPD isoenzymes showed a linear correlation.
Lüthje
J
J
Institut für Physiologische Chemie der Universität Erlangen-Nürnberg, Federal Republic of Germany.
Ogilvie
A
A
D000227:Adenine Nucleotides / Q000097:blood*; D015226:Dinucleoside Phosphates; D006801:Humans; D007527:Isoenzymes / Q000097:blood* / Q000302:isolation & purification; D007700:Kinetics; D043264:Phosphodiesterase I; D010727:Phosphoric Diester Hydrolases / Q000097:blood* / Q000302:isolation & purification
D000227:Adenine Nucleotides; D015226:Dinucleoside Phosphates; D007527:Isoenzymes; C020733:diadenosine tetraphosphate; C011440:diadenosine triphosphate; D010727:Phosphoric Diester Hydrolases; D043264:Phosphodiesterase I