Abstract
Two fractions of glycogen synthase were isolated from rat cardiac muscle on the basis of a different affinity for DEAE-cellulose and omega-aminobutyl-agarose. One of these fractions was able to transfer glucosyl residues from UDP-glucose not only to glycogen (GS-1 activity) but also to an endogenous acceptor. The latter reaction (GS-2 activity) occurred in the absence of added glycogen, and its reaction product was insoluble in trichloroacetic acid. This compound was degraded by amylolytic enzymes, thus showing that the product synthesized on the endogenous acceptor was an alpha 1,4-glucan. After incubation with alpha-amylase-free proteolytic enzyme, the compound was rendered trichloroacetic acid-soluble. Polyacrylamide gel electrophoresis, under both native and denaturing conditions, showed that GS-2 reaction products moved electrophoretically associated to protein. Our results give further evidence for the association between an alpha 1,4-glucan and protein, which we postulate is related to the initiation of glycogen biosynthesis.
Highlights
From the Znstituto de Investigacwnes Bioquimicas “FundacwnCampomar”and the Facultad de Ciencias Exactas y Naturales, Buems Aires, Argentina
Thweith crude enzyme preparations from Neurospora crassa (17, latter reaction (GS-2 activity) occurred in the absence of added glycogen, andits reaction product was insoluble in trichloroacetic acid
This compound was degraded by amylolytic enzymes, showing that the product synthesized on the endogenous acceptor was an al,4-glucan
Summary
From the Znstituto de Investigacwnes Bioquimicas “FundacwnCampomar”and the Facultad de Ciencias Exactas y Naturales, Buems Aires, Argentina. Thweith crude enzyme preparations from Neurospora crassa (17, latter reaction (GS-2 activity) occurred in the absence of added glycogen, andits reaction product was insoluble in trichloroacetic acid. This compound was degraded by amylolytic enzymes, showing that the product synthesized on the endogenous acceptor was an al,4-glucan. The protein-bound glycogen reported in rat heart (22), rat liver (23), rabbit muscle (24), and bovine retina (19) is presumably the same as thatformed in thein vitro experiments. Showed thaGt S-2 reaction products moved electropho- The results obtained with a purified rat heart glycogen retically associated to protein. The biosynthetic origin of glycogen has been postulated to reside in a protein onto which glycogen is built up (11).The in vitro synthesis of glycogen apparently attached
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