Open AccessPurification of a Processing Enzyme (VmPE‐1) that is Involved in Post‐Translational Processing of a Plant Cysteine Endopeptidase (SH‐EP)
Author(s) -
Okamoto Takashi,
Minamikawa Takao
Publication year - 1995
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1995.0300e.x
Subject(s) - endopeptidase , biochemistry , storage protein , cysteine protease , cysteine , protease , enzyme , biology , gel electrophoresis , vigna , molecular mass , proteases , polyacrylamide gel electrophoresis , signal peptidase , signal peptide , peptide sequence , agronomy , gene
A cysteine endopeptidase, designated SH‐EP, occurs in the cotyledons of germinated seeds of Vigna mungo and acts to degrade the seed storage protein in protein storage vacuoles. SH‐EP is synthesized on membrane‐bound ribosomes as an inactive 45‐kDa precursor, which is cotranslationally processed to a 43‐kDa intermediate through cleavage of the signal sequence; the 43‐kDa intermediate of SH‐EP is further processed to the 33‐kDa mature enzyme via 39‐kDa and 36‐kDa intermediates [Mitsuhashi, W. & Minamikawa, T. (1989) Plant Physiol. 89 , 274–279]. The present in vitro processing experiments indicated that at least two processing enzymes, designated VmPE‐1 and VmPE‐2 ( V. mungo processing enzymes 1 and 2), were involved in post‐translational processing, of SH‐EP in cotyledons of V. mungo seedlings. VmPE‐1 was purified from the cotyledons as a protease that was involved in the processing of the 43‐kDa intermediate to the 36‐kDa intermediate. The enzyme has a molecular mass of 33 kDa as estimated by SDS/polyacrylamide gel electrophoresis, and showed high similarity to the jackbean asparaginyl endopeptidase in terms of the primary structure and substrate specificity. We discuss the function of VmPE‐1 in the processing of SH‐EP and related proteases in the cotyledons of germinated seeds.