Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Intracellular fluids of marine elasmobranchs (sharks, skates and rays), holocephalans and the coelacanth contain urea at concentrations averaging 0.4m, high enough to significantly affect the structural and functional properties of many proteins. Also present in the cells of these fishes are a family of methylamine compounds, largely trimethylamine N-oxide with some betaine and sarcosine, and certain free amino acids, mainly beta-alanine and taurine, whose total concentration is approx. 0.2m. These methylamine compounds and amino acids have been found to be effective stabilizers of protein structure, and, at a 1:2 molar concentration ratio of these compounds to urea, perturbations of protein structure by urea are largely or fully offset. These counteracting effects of solutes on proteins are seen for: (1) thermal stability of protein secondary and tertiary structure (bovine ribonuclease); (2) the rate and extent of enzyme renaturation after acid denaturation (rabbit and shark lactate dehydrogenases); and (3) the reactivity of thiol groups of an enzyme (bovine glutamate dehydrogenase). Attaining osmotic equilibrium with seawater by these fishes has thus involved the selective accumulation of certain nitrogenous metabolites that individually have significant effects on protein structure, but that have virtually no net effects on proteins when these solutes are present at elasmobranch physiological concentrations. These experiments indicate that evolutionary changes in intracellular solute compositions as well as in protein amino acid sequences can have important roles in intracellular protein function.
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PMID:Counteraction of urea destabilization of protein structure by methylamine osmoregulatory compounds of elasmobranch fishes. 53 99

A procedure has been developed for the use of metal-ion buffers that depends on the formation of 2:1 complexes between suitable chelators and metal ions. beta-Alanine has been used as the chelator for Cu(2+) ions in a study of Cu(2+) binding by bovine pancreatic ribonuclease by the equilibrium-dialysis technique at pH7.0, 6.1 and 5.2. The results indicated the presence of two avid binding sites, the more avid group being implicated in the inhibition of enzyme activity by Cu(2+) ions. The binding constants of the more avid site were 2.97x10(7), 7.97x10(5) and 1.25x10(4) at pH7.0, 6.1 and 5.2 respectively, and the binding constants of the less avid site were 5.27x10(6) and 1.71x10(5) at pH7.0 and 6.1 respectively. The data show that the Cu(2+) is chelated to the protein through at least two ligand groups on the ribonuclease molecule.
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PMID:The binding of cupric ions to bovine pancreatic ribonuclease studies with diligand metal-ion buffers. 607 Jan 25