Native and Degraded Forms of Sweet Potato Starch Phosphorylase(Biological Chemistry)

概要

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By immunoblotting using monoclonal and polyclonal mouse antibodies against sweet potato(Ipomoea batatas(L.) Lam.) starch phosphorylase(SP), and by activity and dye staining methods, fresh extracts obtained from sweet potatoes immediately after harvest or from those being stored under various conditions were analyzed for SP by PAGE. Freshly prepared pure or crude SP, or those stored under various conditions were also analyzed. We found that the native enzyme from either of the cultivars Tainong 57 or 65 was 220-kDa in size and constituted of two 112-kDa subunits. Either in vivo or in vitro, storage caused degration of the enzyme to two groups of small subunits of about 50-kDa each. On prolonged cold storage of purified enzyme in 50% glycerol, the formation of a small amount of a 250-kDa protein was detected. It had a 150-kDa subunit that was formed presumably by transpeptidation catalyzed by a contaminating protease. This 250-kDa form had the primed SP activity only. The SP from the two kinds of cultivar showed considerable differences in the proteolytic susceptibility and peptide map. A part of Tainong 65 SP was supposed to be a heterodimer.
社団法人日本農芸化学会の論文
1991-03-23