Stimulation by ATP-Mg2+ and inactivation by cyclic-AMP-dependent phosphorylation of a cytosolic monkey brain aminopeptidase.
The activity of a purified cytosolic aminopeptidase (Mr 79,000) from monkey brain was stimulated about 4-fold by ATP-Mg2+. The stimulation was seen with either synthetic aminopeptidase substrates or natural peptides such as enkephalins. Both ATP and Mg2+ were required for stimulation, and ADP did not inhibit the stimulation. Non-hydrolysable analogues of ATP, deoxy-ATP and other nucleoside triphosphates stimulated to a lesser extent compared with ATP, whereas nucleoside mono- or di-phosphates were ineffective. The enzyme did not exhibit any ATPase activity. An ATPase inhibitor, orthovanadate, had no inhibitory effect on the ATP-Mg2+ stimulation. The aminopeptidase was not autophosphorylated by [gamma-32P]ATP and Mg2+, but in the presence of cyclic AMP-dependent protein kinase underwent phosphorylation on serine residue(s). Phosphorylation resulted in inactivation of the aminopeptidase activity, and also resulted in a decreased stimulation of the enzyme by ATP-Mg2+.
Ramamoorthy
S
S
Department of Neurological Sciences, Christian Medical College and Hospital, Vellore, India.
Balasubramanian
A S
AS
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000626:Aminopeptidases / Q000378:metabolism*; D000814:Aniline Compounds / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation; D006863:Hydrogen-Ion Concentration; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*
D000814:Aniline Compounds; C019498:4-nitroaniline; D000255:Adenosine Triphosphate; D011494:Protein Kinases; D000626:Aminopeptidases; D000251:Adenosine Triphosphatases