Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rat liver fructose-1,6-bisphosphatase was phosphorylated with [32P]ATP and the catalytic subunit of cyclic AMP-dependent protein kinase. After digestion with trypsin, two peptides were isolated containing 68 and 32% of the total radioactivity, respectively. The former was found to contain the sequence Ala-Lys-Ser(P)-Arg-Pro-Ser(P)-Leu-Pro. In this fragment, Ser-341, but not Ser-338, had earlier been reported to be a phosphorylation site. The other peptide contained phosphorylated Ser-356. It was demonstrated that all the protein-bound [32P]phosphate was distributed evenly between these three serines in the native enzyme regardless of the degree of phosphorylation. Preservation of the three-dimensional structure, however, was needed to obtain phosphorylation of Ser-356. Peptides containing each phosphorylatable serine residue were sequentially removed by digesting the enzyme with chymotrypsin which cleaved off Ser-356, denaturing it with urea, digesting it further with chymotrypsin, thus removing Ser-341, and finally treating it with trypsin which eliminated the rest of the radioactivity which was bound to Ser-338. Kinetic studies of fructose-1,6-bisphosphatase digested in this manner revealed that phosphorylation of Ser-338 decreased the apparent Km for fructose 1,6-bisphosphatase, whereas phosphorylation of Ser-341 decreased the inhibitory effect of AMP and fructose 2,6-bisphosphatase, Phosphorylation of Ser-356 did not affect these parameters.
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PMID:Rat liver fructose-1,6-bisphosphatase. Identification of serine 338 as a third major phosphorylation site for cyclic AMP-dependent protein kinase and activity changes associated with multisite phosphorylation in vitro. 282 3

Fructose 1,6-bisphosphatase has been purified from rat muscle. Although the specific activity of the enzyme in the crude extract of rat muscle was extremely low, purification by the present procedure is highly reproducible. The purified enzyme showed a single band in SDS-polyacrylamide gel electrophoresis. The subunit molecular weight of the muscle enzyme was 37,500 in contrast to 43,000 in the case of the liver enzyme. Immunoreactivity of the muscle enzyme to anti-muscle and anti-liver fructose 1,6-bisphosphatase sera was clearly distinct from that of the liver enzyme. All one-dimensional peptide mappings of the muscle enzyme with staphylococcal V8 protease, chymotrypsin, and papain showed different patterns from those of the liver enzyme. When incubated with subtilisin, the extent of activation of muscle fructose 1,6-bisphosphatase at pH 9.1 was smaller than that of the liver enzyme. The subtilisin digestion pattern of the muscle enzyme on SDS-polyacrylamide gel electrophoresis was distinct from that of the liver enzyme. The AMP-concentration giving 50% inhibition of the muscle enzyme was 0.54 microM, whereas that of the liver enzyme was 85 microM. The concentrations of fructose 2,6-bisphosphate that gave 50% inhibition of rat muscle and liver enzymes were 6.3 and 1.5 microM, respectively. Fructose 1,6-bisphosphatase protein was not detected in soleus muscle by immunoelectroblotting with anti-muscle fructose 1,6-bisphosphatase serum.
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PMID:Characterization of rat muscle fructose 1,6-bisphosphatase. 301 26

Rat liver fructose 1,6-bisphosphatase appears to be unique in that it extends 24-26 residues beyond the COOH-terminal amino acid of other mammalian fructose 1,6-bisphosphatases and this extension contains phosphorylation sites. Using as a frame of reference the 335-residue sequence of pig kidney fructose 1,6-bisphosphatase (Marcus, F., Edelstein, I., Reardon, I., and Heinrikson, R. L. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 7161-7165), the rat liver enzyme would extend to residue 361. Limited proteolysis in the COOH-terminal region of the molecule with chymotrypsin, trypsin, or both sequentially, led us to establish that the phosphorylation sites are located at Ser residues 341 and 356. The in vitro phosphorylation of purified rat liver fructose 1,6-bisphosphatase by the catalytic subunit of cyclic AMP-dependent protein kinase results in modification at both residues, although the major site of phosphorylation (61%) is at Ser-341. In contrast, rat liver fructose 1,6-bisphosphatase purified from animals that had been injected with [32P] phosphate contains most of the label (81%) at Ser-356.
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PMID:Identification of the in vivo and in vitro phosphorylation sites of rat liver fructose 1,6-bisphosphatase. 632 42