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An analysis of soluble starch synthase isozymes from the developing grains of normal and shx cv. Bomi barley ( Hordeum vulgare )
Author(s) -
Tyynelä Janna,
Schulman Alan H.
Publication year - 1993
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1993.tb05293.x
Subject(s) - amylopectin , hordeum vulgare , starch , starch synthase , isozyme , endosperm , biochemistry , enzyme , chemistry , biology , botany , poaceae , amylose
Soluble starch synthase (SSS, EC 2.4.1.21) catalyzes formation of the α‐1,4 bonds of amylopectin. It occurs in multiple isozymes which are either type I, primer‐independent in the presence of citrate, or type II. always primer‐dependent. To analyze the enzyme. a sensitive native gel assay was developed, monitoring ADP‐[ 14 C]glucose incorporation into insoluble α‐glucan in the presence of either sodium citrate or glycogen primer or both. Using this system, we observed multiple type I and type II forms in developing grains of barley ( Hordeum vulgare L.) cv. Bomi, the relative activities of which vary with seed development. At least one form comigrates in native gels with starch branching enzyme. Assays of the shx mutant, which is severely reduced in starch accumulation and in type I SSS activity, indicate that one type I isozyme becomes primer‐dependent.