Abstract
Carboxypeptidase Y (CPY) inhibitor (IC) and its homologous protein (ICh) are thought to be members of the phosphatidylethanolamine-binding protein (PEBP) family of Saccharomyces cerevisiae. The biochemical characterization of IC and its inhibition mode toward CPY were recently reported, but ICh has not been characterized. The molecular mass of ICh was determined to be 22,033.7. The N-terminal Met1 was cleaved and the amino group of Ser2 was acetylated. ICh is folded as a monomeric β-protein and is devoid of disulfide bonds. It has no inhibitory activity toward CPY, and it does not form a complex with CPY. ICh was exclusively expressed in the early log phase, whereas IC was expressed in the logarithmic and stationary phase. The intracellular localization of ICh was different from that of IC. These findings provide insights into the physiological functions of ICh.
