Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have tested rat liver fructose-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) and three other gluconeogenic fructose-bisphosphatases as substrates for the catalytic subunit of cyclic AMP-dependent protein kinase. In contrast to the rat liver enzyme, homogeneous preparations of mouse liver, rabbit liver, and pig kidney fructose-bisphosphatase could not be phosphorylated by the kinase. Comparative sodium dodecyl sulfate/polyacrylamide gel electrophoresis of the four above fructose-bisphosphatases revealed that the subunit molecular weight of the isolated rat liver enzyme (ca. 40,000-42,000) was greater than that of mouse liver, rabbit liver, and pig kidney fructose-bisphosphatases (ca. 36,000-37,000). Treatment of 32P-labeled rat liver fructose-bisphosphatase with trypsin resulted in the conversion of the rat liver enzyme to an active species with a subunit molecular weight identical to that of the three other enzymes, with complete loss of the 32P-labeled site. Identical trypsin treatment of pig kidney fructose-bisphosphatase caused no change in the molecular weight of the enzyme. The results suggest that the purified mouse liver, rabbit liver, and pig kidney fructose-bisphosphatases are not substrates for the cyclic AMP-dependent protein kinase in vitro because they lack the phosphorylation-site peptide.
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PMID:Fructose-bisphosphatase as a substrate of cyclic AMP-dependent protein kinase. 626 56

Phosphorylation of fructose-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) by the catalytic subunit of cyclic AMP-dependent protein kinase from pig muscle decreased the K0.5 for fructose-bisphosphate from 21 to 11 microM. When the phosphorylated fructose-bisphosphatase was treated with trypsin the K0.5 increased to 22 microM. The K0.5 also increased when the phosphoenzyme was treated with a partially purified phosphatase from rat liver. There was no difference between the unphosphorylated and phosphorylated enzyme with respect to pH dependence, the pH optimum being about 7.0 for both. Limited treatment of fructose-bis-phosphatase with subtilisin, which cleaves the enzyme at its unphosphorylatable N-terminal part, increased the pH optimum more than limited treatment with trypsin, which releases the phosphorylated peptide at the C-terminal part of fructose-bisphosphatase. The phosphorylated site on the phosphorylated fructose-bisphosphatase was more easily split off by trypsin treatment than the corresponding unphosphorylated site. The results suggest in addition to the glucagon-induced phosphorylation of fructose-bisphosphatase described by Claus et al. [1] that the phosphorylation-dephosphorylation of fructose-bisphosphatase could be of importance for the hormonal regulation of the enzyme in vivo.
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PMID:The kinetics of unphosphorylated, phosphorylated and proteolytically modified fructose bisphosphatase from fat liver. 627 12