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Isolation of partial cDNAs for rat liver and muscle glycogen phosphorylase isozymes
Author(s) -
Osawa Shoji,
Chiu Robert H.,
McDonough Alicia,
Miller Thomas B.,
Johnson Gary L.
Publication year - 1986
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(86)80702-5
Subject(s) - isozyme , glycogen phosphorylase , biochemistry , glycogen debranching enzyme , isolation (microbiology) , glycogen , chemistry , phosphorylase kinase , biology , microbiology and biotechnology , enzyme , bioinformatics
cDNA clones for the rat liver and muscle glycogen phosphorylase isozymes have been isolated using isozyme‐selective antibodies and libraries prepared in the expression vector, λgt11. A 1.2 kb cDNA coding for the carboxy‐terminal domain of rat liver phosphorylase was found to have 82% homology with the amino acid sequence of rabbit muscle phosphorylase. Limited sequencing of rat muscle phosphorylase cDNA indicated a 95% homology with the rabbit muscle enzyme. The rat liver clone has eight additional amino acid residues at the COOH‐terminus compared to the rat muscle clone. Furthermore, 17 of 26 (65%) residues between amino acids 815–840 differ between liver and muscle isozymes. The similarity in enzymatic properties and conservation of structure except at the COOH‐terminus suggest that the liver and muscle phosphorylase isozymes do not exist in order to have significant differences in the regulation of glycogen breakdown in the two tissues. Rather, the phosphorylase isozymes probably evolved for tissue‐specific transcriptional regulation of the genes in liver and muscle.