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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reactions of glycine with inorganic polyphosphates in the solid state have been studied. The formation of peptides up to the decamer occurs at moderate temperatures(r.t.-100 degrees C) in the presence of imidazole and magnesium chloride. If adenosine 5' -monophosphate is added to the reaction mixture, 2'(3') -o-glycyl adenosine 5'-monophosphate is also obtained. These reactions could have occurred on the primitive earth.
J Mol Evol 1975 Nov 04
PMID:Prebiotic peptide-formation in the solid state. III. Condensation reactions of glycine in solid state mixtures containing inorganic polyphosphates. 0 39

A reaction which oligomerizes nucleotides under possible prebiotic conditions has been characterized. Nucleoside monophosphate in the presence of cyanamide at acid pH condenses to form dithymideine pyrophosphate and phosphodiester bonded compounds. Imidazole compounds and activated precursors such as nucleoside triphosphate are not necessary for this ologomerization reaction which produces primarily cyclic ologonucleotides.
J Mol Evol 1975 Nov 04
PMID:The prebiotic synthesis of deoxthymidine oligonucleotides. II. Comparison of condensing agents. 0 40

When solutions of nucleoside 5'-phosphates and trimetaphosphate are dried out at room temperature, nucleoside 5'-polyphosphates are formed. The Mg++ ion shows a superior catalytic function in this reaction when compared with other divalent metal ions. Starting with nucleoside 5'-phosphates, Mg++ and trimetaphosphate, the predominant products in the nucleoside 5'-polyphosphate series pnN are p4N, P7N and p10N. Nucleoside 5'-diphosphates yield p5N and p8N, nucleoside 5'-triphosphates give p6N and p9N. The prebiological relevance of these reactions is discussed.
J Mol Evol 1975 Dec 29
PMID:Formation of nucleoside 5'-polyphosphates from nucleotides and trimetaphosphate. 0 41

One of the major diagenetic pathways of organic matter in recent sediments involves the condensation of cellular constituents, particularly amino acids and sugars, into insoluble melanoidin-type polymers. These polymers consist mainly of humic and fulvic acids and make up the major part of the organic carbon reservoir in recent sediments. We suggest that a similar set of reactions between abiotically formed amino acids and sugars, and more generally between aldehydes and amines, occurred on a large scale in the prebiotic hydrosphere. The rapid formation of this insoluble polymeric material would have removed the bulk of the dissolved organic carbon from the primitive oceans and would thus have prevented the formation of an "organic soup". Melanoidin polymers have several properties which make them attractive hypothetical precursors of contemporary oxidation-reduction coenzymes: 1. they contain heterocyclic nitrogen compounds similar to the nitrogenous bases; 2. they contain a high concentration of stable free radicals; and 3. they tend to concentrate those heavy metals which play prominent roles in contemporary enzymic redox processes. The prebiotic formation of similar polymers could, therefore, have provided the starting point for a basic class of biochemical reactions. We suggest that the prebiotic scenario involved chemical and protoenzymic reactions at the sediment-ocean interface in relatively shallow waters and under conditions not much different from those of the recent environment.
J Mol Evol 1975 Dec 29
PMID:On the possible role of organic melanoidin polymers as matrices for prebiotic activity. 0 42

Comparative data on quaternary structure, cooperativity, Bohr effect and regulation by organic phosphates are reviewed for vertebrate hemoglobins. A phylogeny of hemoglobin function in the vertebrates is deduced. It is proposed that from the monomeric hemoglobin of the common ancestor of vertebrates, a deoxy dimer, as seen in the lamprey, could have originated with a single amino acid substitution. The deoxy dimer has a Bohr effect, cooperativity and a reduced oxygen affinity compared to the monomer. One, or two, additional amino acid substitutions could have resulted in the origin of a tetrameric deoxy hemoglobin which dissociated to dimers on oxygenation. Gene duplication, giving incipient alpha and beta genes, probably preceded the origin of a tetrameric oxyhemoglobin. The origin of an organic phosphate binding site on the tetrameric hemoglobin of an early fish required only one, or two, amino acid substitutions. ATP was the first organic phosphate regulator of hemoglobin function. The binding of ATP by hemoglobin may have caused the original elevation in the concentration of ATP in the red blood cells by relieving end product inhibition of ATP synthesis. The switch from regulation of hemoglobin function by ATP to regulation by DPG may have been a consequence of the curtailment of oxidative phosphorylation in the red blood cell. The basic mechanisms by which ATP and DPG concentrations can respond to strss on the oxygen transport system were present before the origin of an organic phosphate binding site on hemoglobin. A switch from ATP regulation to IP5 regulation occurred in the common ancestor of birds.
J Mol Evol 1975 Dec 29
PMID:Hemoglobin function in the vertebrates: an evolutionary model. 0 43

Imidazole catalysis of phenylalanyl transfer from phenylalanine adenylate anhydride to the hydroxyl groups of homopolyribonucleotides was investigated as a chemical model of the biochemical aminoacylation of tRNA. Imidazole catalyzed transfer of phenylalanine to poly(U) increases from pH 6.5 to 7.7 and decreases above pH 7.7. At pH 7.7 approximately 10% of the phenylalanyl residues are transferred to poly(U). At pH 7.1, transfer to poly(U) was five times as great as to poly(A) and transfer to a poly(A) poly(U) double helix was negligible. At pH 7.1 approximately 45 mole percent linkages to poly(U) were monomeric phenylalanine; the remainder of the linkages were peptides of phenylalanine. The number of linkages and their lability to base and neutral hydroxylamine indicates that phenylalanine and its peptides are attached as esters to the 2' hydroxyl groups throughout poly(U) and the 2' (3') hydroxyl groups at the terminus of poly(U). These results do model the contemporary process of aminoacyl transfer to tRNA and continue to suggest that a histidine residue is in the active site of aminoacyl-tRNA-synthetases.
J Mol Evol 1975 Dec 29
PMID:Aminoacyl transfer from an adenylate anhydride to polyribonucleotides. 0 44


Mol Pharmacol 1975 Nov
PMID:Turnover rate of tyrosine hydroxylase during Trans-synaptic induction. 0 66


Mol Pharmacol 1975 Nov
PMID:A re-evaluation of the optical titrations of the 430 and 455 nm chromophore of ethyl isocyanide complexes of mamalian hepatic cytochrome P-450. 0 67


Mol Pharmacol 1975 Nov
PMID:Hepatic microsomal alcohol-oxidizing system in normal and acatalasemic mice: its dissociation from the peroxidatic activity of catalase-H2O2. 0 68

The kinetics of the transformation of poly(L-tyrosine) from the disordered chain to the intramolecular beta structure in aqueous solution has been studied. The reaction is induced by an isothermal pH jump and is followed by conventional circular dichroism methods. Upon application of curve-fitting procedures, it is found that the kinetics are poorly represented by a single first-order process, but a two-step sequential first-order equation is adequate. Sharp pH-dependent maxima in the phenomenological rate constants and in the fractional amplitude of the rapid step were found. It is proposed to attribute these phenomena to a transition in initial states which is shown to occur over the same pH range within the domain of the disordered-to-beta transition. No sigmoid transient curves were observed, indicating that no slow nucleation events are discernible in this system. These observations contrast strikingly with the mechanism elaborated for beta formation in (Lys)n [R. Hartman et al., J. Mol. Biol. 90 (1974) 415].
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PMID:Kinetics of the disordered chain-to-beta transformation of poly(L-tyrosine) in aqueous solution. 0 46


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