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)

Alanyl-tRNA synthetase from Escherichia coli, Bombyx mori and rat were examined with respect to the following functional and structural properties: the effect of substrates on sensitivity to proteolysis, secondary structure as determined by circular dichroism, amino acid composition and, in the case of the rat and insect enzymes, partial amino acid sequence determination on a 60-kDa C-terminal tryptic fragment. Digestion of the enzyme from all three sources with trypsin resulted in significant decline in aminoacyl-tRNA synthetase activity with little effect on pyrophosphate-exchange activity. In each case the presence of alanine and ATP together, but not separately, reduced the rate of digestion by trypsin; the largest effect was observed with the enzyme from rat liver. Trypsin digestion generated fragments of 47 kDa and 40 kDa with all three enzymes, but detection of significant quantities of the 47-kDa fragment from the rat enzyme required the presence of ATP and alanine. Trypsin digestion produced a fragment of 60 kDa with all three enzymes, but detection of significant quantities of this fragment with the bacterial enzyme required the presence of ATP and alanine. Limited sequence analysis of the 60-kDa fragment from the insect and rat enzymes indicated that trypsin cleaved both proteins at the same site to generate this species. Similar effects of substrates were observed when the enzymes were digested with chymotrypsin suggesting that the effects of substrates on protease sensitivity were not unique to trypsin. Circular dichroism spectra obtained for the three enzymes were qualitatively and quantitatively similar. There is some similarity in amino acid composition between the rat and insect enzymes.
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PMID:Alanyl-tRNA synthetase from Escherichia coli, Bombyx mori and Ratus ratus. Existence of common structural features. 204 Feb 80

Alanyl-tRNA synthetase of 115K daltons from Bombyx mori was cleaved into two fragments of 62K and 47K daltons by trypsin. The 47K fragment was active in aminoacylation of tRNA, whereas the 62K fragment was inactive. The 47K and 62K fragments were found to be located at the N- and C-terminal ends, respectively, in the intact enzyme. The intact enzyme was protected from trypsin-attack by the cognate tRNA. The Km value of the 47K fragment for tRNA was 22 microM which is about 16-fold higher than that for the intact enzyme (1.4 microM). The molecular activities of the fragment and the intact enzyme were 2.2 s-1 and 16.8 s-1, respectively. This indicates that the 62K domain enhances affinity for tRNA and it is responsible for the full activity of tRNA aminoacylation. These results do not support the "covalently linked dimer" hypothesis, but indicate that the alanyl-tRNA synthetase is a functional monomer consisting two large domains.
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PMID:Two-domain structure of alanyl-tRNA synthetase from Bombyx mori: isolation of the N-terminal catalytic domain. 609 58

Alanyl-tRNA synthetase of 115K dalton from Bombyx mori was cleaved into two fragments of 68K and 47K dalton with trypsin. The 47K fragment was active in aminoacylation of tRNA, whereas the 68K fragment inactive. The 47K and 68K fragments were located at the N- and C- terminal sides, respectively, in the intact enzyme. When the enzyme binds alanine specific tRNA, the tryptic digestion is inhibited. The Km value of the 47K fragment for tRNA was about 16-fold higher than that (1.4 microM) of the intact enzyme. The molecular activities of the 47K fragment and the intact enzyme were 2.2/sec and 16.8/sec, respectively. These results show that 1) Bombyx mori alanyl-tRNA synthetase functions in a monomeric state and 2) the C-terminal domain enhances affinity for tRNA and is responsible for full activity of aminoacylation.
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PMID:Domain-structure of large monomeric alanyl-tRNA synthetase from Bombyx mori: evidence of a single catalytic domain. 652 83