Abstract
Novel microsomal cysteine proteases, ER-60 and ER-72 proteases, were purified. ER-60 and ER-72 proteases are defined as a new type of cysteine protease localized in the endoplasmic reticulum. The open reading frame of ER-60 protease cDNA encodes 505 amino acid residues. The amino acid sequence was similar to that of phosphoinositide-specific phospholipase Cα, but the sequence corresponding to Ile232-Ile240 of ER-60 protease was different from the corresponding region of phosphoinositide-specific phospholipase Cα in the amino acid species and numbers. From the results of analysis with cysteine protease inhibitors and the distribution in organs, ER-60 and ER-72 proteases are assumed to participate in qualitative and quantitative control of ER synthesized proteins.
