In vitro translation of intestinal sucrase-isomaltase and glucoamylase.
It is has been proposed that both sucrase-isomaltase and glucoamylase are initially synthesized as large single-chain precursors which are then processed to heterodimers. We have tested this hypothesis by in vitro translation of their mRNAs. The primary translation product of sucrase-isomaltase mRNA was a single polypeptide of Mr = 190,000. Similar experiments using antiserum against glucoamylase revealed a single polypeptide of Mr = 145,000. These results are consistent with the single chain precursor hypothesis for sucrase-isomaltase. However, the glucoamylase product (145 kDa) is too small to be processed to a heterodimer of Mr = 230,000. Moreover, the mature subunits (Mr = 135,000 and 125,000) probably are derived from the 145 kDa precursor by proteolytic trimming and must include and share most of the precursor protein.
Alpers
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DH
Helms
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Seetharam
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May
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Strauss
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D000818:Animals; D004591:Electrophoresis, Polyacrylamide Gel; D005087:Glucan 1,4-alpha-Glucosidase / Q000096:biosynthesis*; D005959:Glucosidases / Q000096:biosynthesis*; D007422:Intestines / Q000201:enzymology*; D008970:Molecular Weight; D009097:Multienzyme Complexes / Q000096:biosynthesis*; D014176:Protein Biosynthesis; D051381:Rats; D013394:Sucrase-Isomaltase Complex / Q000096:biosynthesis*
D009097:Multienzyme Complexes; D005959:Glucosidases; D013394:Sucrase-Isomaltase Complex; D005087:Glucan 1,4-alpha-Glucosidase