N-terminal acetyl group is essential for the inhibitory function of carboxypeptidase Y inhibitor (I(C)).
Carboxypeptidase Y (CPY) inhibitor, I(C), a yeast cytoplasmic inhibitor in which the N-terminal amino acid is acetylated, was expressed in Escherichia coli and produced as an unacetylated form of I(C) (unaI(C)). Circular dichroism and fluorescence measurements showed that unaI(C) and I(C) were structurally identical and produce identical complexes with CPY. However, the K(i) values for unaI(C) for anilidase and peptidase activity of CPY were much larger, by 700- and 60-fold, respectively, than those of I(C). The reactivities of phenylmethylsulfonyl fluoride and p-chloromercuribenzoic acid toward the CPY-unaI(C) complex were considerably higher than those toward the CPY-I(C) complex. Thus, the N-terminal acetyl group of I(C) is essential for achieving a tight interaction with CPY and for its complete inactivation.
Mima
Joji
J
Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan. mima@kais.kyoto-u.ac.jp
Kondo
Takahiro
T
Hayashi
Rikimaru
R
D000107:Acetylation; D002268:Carboxypeptidases / Q000378:metabolism*; D043402:Cathepsin A; D002850:Chromatography, Gel; D002942:Circular Dichroism; D004926:Escherichia coli / Q000235:genetics; D005453:Fluorescence; D011480:Protease Inhibitors / Q000737:chemistry* / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism
D011480:Protease Inhibitors; D029701:Saccharomyces cerevisiae Proteins; D002268:Carboxypeptidases; D043402:Cathepsin A