Soluble starch synthases forms

Multiple forms of soluble starch synthases are present in barley endosperm,178 pea seeds,43 179 wheat endosperm,180482 maize endosperm,174 183-186 potato tuber,187 189 Arabidopsis,190 rice seed,191 192 Chlamydomonas reinhardtii,m sorghum seeds, teos-inte seeds and spinach leaf (the latter three are reviewed in references 2,7 and 27). 

Amylose is synthesized by granular-bound starch synthase, whereas amylopectin is synthesized by soluble starch synthase (Chapter 4).334,339 Because amylose is synthesized by the granular-bound starch synthase in a progressive manner,340 the amylose molecule is likely confined in the granule and has little opportunity to interact and form double helices with other starch molecules to facilitate branch formation. Branching reactions do occur on some amylose molecules, but at a much lower frequency than with amylopectin, and result in slightly branched amylose molecules. 

Multiple forms of soluble starch synthases are observed in barley endosperm,... 

TANAKA, K., OHNISHI, S., KISHIMOTO, N., KAWASAKI, T., BABA, T Structure, organization, and chromosomal location of the gene encoding a form of rice soluble starch synthase. Plant Physiol, 1995,108,677-683. 

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