A comparison of guinea pig serum angiotensin converting enzyme with forms of angiotensin converting enzyme from human, rat and rabbit tissues.
Guinea pig serum angiotensin converting enzyme (ACE) activities exceed ACE activities of other mammalian sera by as much as two magnitudes. To examine the possibility that guinea pig ACE has a superior catalytic efficiency, we purified it to apparent homogeneity and compared it to highly purified forms of ACE from human seminal plasma, rat lungs and rabbit lungs. The first 24 amino acid residues of guinea pig and rat ACE forms were 96% identical with the sequence of human ACE. Second order rate constants (kcat/Km) for guinea pig, human and rabbit forms of ACE on reaction with benzoyl-Phe-Ala-Pro were identical (1.6E-09 M-1 min-1). Their dissociation constants on reaction with the ACE inhibitor RAC-X-65 were within a narrow range (10-16 pM). Thus, the high ACE activity of guinea pig serum is owing to high enzyme concentration and not to superior catalytic efficiency.
Ryan
J W
JW
Department of Medicine, University of Miami School of Medicine, FL 33101.
Valido
F A
FA
Chung
A Y
AY
Ripka
J E
JE
Peterson
C M
CM
Urry
R L
RL
D000595:Amino Acid Sequence; D000818:Animals; D002151:Calorimetry; D016384:Consensus Sequence; D006168:Guinea Pigs; D006801:Humans; D007527:Isoenzymes / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008168:Lung / Q000201:enzymology*; D008297:Male; D008969:Molecular Sequence Data; D007703:Peptidyl-Dipeptidase A / Q000097:blood / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D012661:Semen / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid
D007527:Isoenzymes; D007703:Peptidyl-Dipeptidase A