Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17174 (aspartate aminotransferase)
 14,872 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In embryos of loach (Misgurnus fossilis) obtained from zygotes, which were incubated for 30 min in the D,L-aspartate solution the alanine aminotransferase activity is 2-4 times as high as in the control embryos. The most essential influence of this amino acid is found in the gastrula -- from 12 till 18 h after fertilization. The aspartate aminotransferase activity under these conditions does not undergo the essential changes. D,L-alanine and adenine do not affect the activity of the both enzymes during primary stages of development, but adenine as well as cytidine reduce the action of aspartate carbamoyltransferase of embryos 3, 6 and 3 h after the beginning of fertilizatio, respectively. The decrease in the aspartate carbamoyltransferase activity is revealed in the unfertilized eggs after 2 h of incubation in the solutions of estrone and thyroxine. Cytidine alone under these conditions has no definite influence, but removes the inhibitory effect of estrone. The regularities were established in changes of the activity of above mentioned enzymes of embryos under physiological conditions of development.
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PMID:[Activity of aspartate carbamoyltransferase, alanine and aspartate aminotransferases in loach embryos after incubation of zygotes in solutions of bioorganic compounds]. 124 Jun 68

Genetic engineering is a powerful tool for exploring correlations between structure and function in proteins, but as yet we are unable to use it for effective protein design. One of the most interesting examples, which would seem to be obvious, is reversing the polarity of an ion pair. Changing a positively charged protein group, that provides a strong binding for negative substrates, to a negative group is expected to provide an effective binding site for a positively charged substrate. But several recent experiments on aspartate aminotransferase, trypsin and aspartate transcarbamoylase (Schachman, H. K. personal communication) have indicated that polarity reversal is not so successful. Here we argue that the same factors that make the enzyme an effective system for the (-+) pair will make it a much less effective system for the (+-) pair. We also point out that the unusually low effective dielectric constant (epsilon approximately equal to 13) for the (-+) interaction is due to its microenvironment and this will destabilize a (+-) arrangement having an entirely different dielectric constant (epsilon approximately equal to 80). The calculations presented here evaluate the energetics of ion pairs in protein active sites on a semiquantitative level. This is particularly important when dealing with strong, functionally important interactions that are difficult to evaluate with macroscopic models.
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PMID:Why ion pair reversal by protein engineering is unlikely to succeed. 316 61

Understanding the molecular mechanisms of enzyme catalysis and allosteric regulation has been a primary goal of biochemistry for many years. The dynamics of these processes, approached through a variety of kinetic methods, are discussed. The results obtained for many different enzymes suggest that multiple intermediates and conformations are general characteristics of the catalytic process and allosteric regulation. Ribonuclease, dihydrofolate reductase, chymotrypsin, aspartate aminotransferase, and aspartate transcarbamoylase are considered as specific examples. Typical and maximum rates of conformational changes and catalysis are also discussed, based on results obtained from model systems. The nature and rates of interconversion of the intermediates, along with structural information, can be used as the bases for understanding the incredible catalytic efficiency of enzymes. Potential roles of conformational changes in the catalytic process are discussed in terms of static and environmental effects, and in terms of dynamic coupling within the enzyme-substrate complex.
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PMID:Multiple conformational changes in enzyme catalysis. 1208 70