5-Ketofructose reductase [D(-)fructose:(NADP+) 5-oxidoreductase] was purified to homogeneity from Erwinia citreus and demonstrated to catalyse the reversible NADPH-dependent reduction of 5-ketofructose (D-threo-2,5-hexodiulose) to D-fructose. The enzyme appeared as a single species upon analyses by SDS/polyacrylamide-gel electrophoresis and isoelectric focusing with an apparent relative molecular mass of 40,000 and an isoelectric point of 4.4. The amino acid composition of the enzyme and the N-terminal sequence of the first 39 residues are described. The steady-state kinetic mechanism was an ordered one with NADPH binding first to the enzyme and then to 5-ketofructose, and the order of product release was D-fructose followed by NADP+. The reversible nature of the reaction offers the possibility of using this enzyme for the determination of D-fructose.
The steady-state kinetic mechanism of the reaction catalyzed by octopine dehydrogenase [N2-(1-carboxyethyl)-L-arginine:NAD+ oxidoreductase] was investigated at pH 6.9 and 9.2 by studies of substrate inhibition, analogue inhibition, and product inhibition. In the direction of octopine synthesis, the inhibition patterns in the presence of delta- guanidinovalerate and propionate show that NADH binds to the enzyme first followed by L-arginine and pyruvate which bind randomly. In the direction of octopine oxidation, the substrate patterns show that NAD binds to the enzyme before octopine in a rapid equilibrium fashion, and the product inhibition patterns show that the products L-arginine and pyruvate are released in a random fashion. Double, synergistic, substrate inhibition by L-arginine and pyruvate was shown to be due to binding (hypothetically of the imine) to the free enzyme and the enzyme-NAD complex. Furthermore, an alternate minor pathway was demonstrated which includes an enzyme-NADH-octopine complex and an enzyme-octopine complex.
Nopaline (N-[4-[(aminoirninomethyl)amino-]-lScarboxybutyll-2 R-aminopentanedioic acid and isonopaline (N-[4-[(aminoiminomethyl)amino-]-1S-carboxybutyl]-2S-aminopentanedioic acid) have been synthesized and separated by crystallization.In addition, a derivative of each of these compounds that forms spontaneously from the parent compounds under the usual crystallization conditions was isolated and characterized.The chemical properties, elemental analysis, 'H-NMR spectrum, and electrophoretic behavior of the derivative from nopaline are consistent with N44-[(aminoiminomethyl)amino]-1S-carboxybutyl]-2-pyrrolidone-5R-carboxylic acid, also called pyronopaline.The presence of pyronopaline in crown gall tumor tissue and the catabolism of it by the bacterium A. tumefaciens establish it as a new opine.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIsolation of a multifunctional protein with aminoimidazole ribonucleotide synthetase, glycinamide ribonucleotide synthetase and glycinamide ribonucleotide transformylase activities: characterization of the aminoimidazole ribonucleotide synthetaseJ. L. Schrimsher, F. J. Schendel, and J. StubbeCite this: Biochemistry 1986, 25, 15, 4356–4365Publication Date (Print):July 1, 1986Publication History Published online1 May 2002Published inissue 1 July 1986https://doi.org/10.1021/bi00363a027Request reuse permissionsArticle Views162Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alertsclose Get e-Alerts
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