A novel aminopeptidase with highest preference for lysine.
Neuropeptides are formed from sedentary precursors to smaller, active peptides by processing enzymes cleaving at paired basic residues. The process generates peptide intermediates with additional Lys or Arg residues at their NH(2) and COOH termini; the N-terminal basic amino acids are later removed by specific aminopeptidases. We report here a novel lysine-specific aminopeptidase (KAP) of ubiquitous distribution. The enzyme was resolved from puromycin-sensitive aminopeptidase (PSA), aminopeptidase B (APB), and neuron-specific aminopeptidase (NAP). It was purified by FPLC after (NH(4))(2)SO(4) precipitation. The purified KAP had a K(m) of 333 microM with a V(max) of 0.7 nmol Lys ssNA/min/mg protein. N-terminal basic amino acids, Lys in particular, were its favorable substrates. KAP was inhibited by chelating agents and by serine protease inhibitors. It was highly sensitive to aminopeptidase inhibitor bestatin, but insensitive to puromycin and amastatin, showing that KAP is distinct from PSA, NAP, and aminopeptidase A (APA). The 62,000-Da enzyme had a pH optimum at 7.5 and NaCl was its strongest activator. However, metals could not restore KAP's activity after it was dialyzed against EGTA. Our data indicated that rat KAP did not resemble any aminopeptidases as well as the microbial lysine aminopeptidases.
Hui
Maria
M
Peptide Research Laboratory, Neurochemistry Division, Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, 10962, USA.
Hui
Koon-Sea
KS
D000626:Aminopeptidases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008239:Lysine / Q000378:metabolism*; D008297:Male; D008970:Molecular Weight; D009479:Neuropeptides / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013379:Substrate Specificity; D014018:Tissue Distribution
D004791:Enzyme Inhibitors; D009479:Neuropeptides; D000626:Aminopeptidases; C056860:lysyl aminopeptidase; D008239:Lysine