The relationships among and the properties of the pyruvate kinase isozymes are reviewed, emphasizing their potential role in carcinogenesis. Particular consideration is given to evaluation of the concept that the three major nonreadily interconvertible forms are the products of distinct genes, the relationship of these forms to additional separable forms of pyruvate kinase, the types and possib...

Protein conformational heterogeneity and dynamics are known to play an important role in enzyme catalysis, but their influence has been difficult to observe directly. We have studied the effects of heterogeneity in the catalytic reaction of pig heart lactate dehydrogenase using isotope edited infrared spectroscopy, laser-induced temperature jump relaxation, and kinetic modeling. The isotope edi...

Growth of microorganisms on substitutable substrate mixtures display diverse growth dynamics characterized by simultaneous or preferential uptake of carbon sources. This article shows that cybernetic modeling concepts which were successful in predicting diauxic growth patterns can be extended to describe simultaneous consumption of substrates. Thus the growth of Escherichia coli on mixtures of ...

In a condensation between [3-3H3]pyruvate and D-glyceraldehyde-3-P as catalyzed by 2-keto-3-deoxygluconate-6-P aldolase (EC 4.1.2.14) of Pseudomonas putida, C--C synthesis occurred appreciably faster than C--3H bond breaking. Since tritium is present in tritiated pyruvate in tracer amounts, this result showed hydrogen isotope discrimination in pyruvate deprotonation and suggests enolpyruvate ge...

The kinetics of pyruvate kinase from Saccharomyces cerevisiae were studied in assays at pH 6.2 where the relationships between the initial velocities of the catalysed reaction and the concentrations of the substrates ADP, phosphoenolpyruvate and Mg2+ are non-hyperbolic. The findings were represented empirically by the exponential model for a regulatory enzyme. The analysis shows that ADP, phosp...

The E. coli pyruvate and 2-oxoglutarate dehydrogenases are two closely related, large complexes that exemplify a growing number of multiprotein "machines" whose domains have been studied extensively and modeled in atomic detail, but whose quaternary structures have remained unclear for lack of an effective imaging technology. Here, electron cryotomography was used to show that the E1 and E3 sub...

It was previously observed (1) that the animal carboxylase enzyme system that converts pyruvate to acetoin can utilize acetaldehyde in this reaction. Other aldehydes are also utilized in the formation of analogous ketols, and the reaction between pyruvate and propionaldehyde results in a 5-carbon ketol according to Reaction I or II. The exact location of the carbonyl and hydroxyl groups in the ...

Aerotolerance in the growth of Streptococcus mutans and related streptococci was examined under glucose-limited conditions. The growth rate of all strains tested was more or less retarded when they were transferred from anaerobic to aerobic conditions. As for growth yield, however, some strains (group 1) showed reduced values for the increment of cellular dry weight change (in grams per mole of...

A simple automated fluorometric method for the estimation of lactate and pyruvate is described. Analyses can be performed at 60/hour and can conveniently determine pyruvate and lactate in the ranges 0-5 mg. and 0-30 mg/100 ml. The methods give a high degree of analytical precision and good yields from recovery experiments.

The low carbon-13/carbon-12 ratio of lipids is shown to result from isotopic fractionation during the oxidation of pyruvate to acetyl coenzyme A. In vitro analysis of the kinetic isotope effects of this reaction indicates that there will be a large, temperature-dependent difference in the carbon-13/carbon-12 ratio between the methyl and carbonyl carbon atoms of acetyl coenzyme A and between tho...