Two Novel Endopeptidases Released into the Medium during Mating of Gametes of Chlamydomonas reinhardtii : PROTEINS, ENZYMES AND METABOLISM : CELL-CELL INTERACTION

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During the mating reaction between mt^+ and mt^- gametes of Chlamydomonas reinhardtii, two novel endopeptidases, each of which was able to digest the B chain of insulin, were released into the culture medium, together with a gamete lytic enzyme (GLE) which is responsible for digestion of the gametic cell walls. Both endopeptidases and GLE were copurified from the mating medium by column chromatography on DEAE-cellulose and concanavalin A. Gel filtration separated the peptidases, which were unable to digest gametic cell walls, into two fractions, endopeptidase-1 and endopeptidase-2. These enzymes were also separated from GLE, which was unable to digest the B chain of insulin. Endopeptidase-1 , with a molecular mass of about 200 kDa, cleaved the B chain of insulin at the Ala^<14>-Leu^<15> peptide bond, and this activity was inhibited by EDTA. Endopeptidase-2, with a molecular mass of about 1 10 kDa, digested the peptide at the Leu^<15>-Tyr^<16> peptide bond and was sensitive to iodoacetate and chymostatin. When the cell walls of gametes of either mating-type were digested prior to mating with exogenously added GLE, the two endopeptidases were released into the medium, a result that suggests that they are stored, like GLE, outside the plasmalemma.
日本植物生理学会の論文