Gamma-Glutamyltransferase: kinetic properties and assay conditions when gamma-glutamyl-4-nitroanilide and its 3-carboxy derivative are used as donor substrates.

The kinetics of human serum gamma-glutamyltransferase (EC 2.3.2.

Determination of the mechanism and kinetic constants for hog kidney gamma-glutamyltransferase.

The initial-velocity kinetics of hog kidney gamma-glutamyltransferase were studied. Glutamate gamma-(4-nitroanilide) and its 3-carboxy derivative, glutamate gamma-(3-carboxy-4-nitroanilide), served as gamma-glutamyl donors, and glycylglycine as an acceptor. Reaction products were identified by paper chromatography and amino acid analysis.

A.E. Bennett Award Paper. A kinetic analysis of 5-hydroxyindoleacetic acid excretion from rat brain and csf.

Studies of neurotransmitter kinetics based on intraventricular injections of radio-labeled metabolites have been limited by several problems, including the inability of most investigators to recover more than 45% of the infected isotope from brain homogenates within several minutes after the injection...

A systematic approach to enzyme assay optimization illustrated by aminotransferase assays.

We have developed a systematic approach to optimization of reagent concentrations for assays of alanine aminotransferase and aspartate aminotransferase: (a) Michaelis constants describing the initial-velocity kinetics of the coupled enzyme reactions were evaluated by a nonlinear least-squares fit of the appropriate equation to measured enzyme activities. Activities of more than 50 normal and pathological sera were measured at 30 degrees C. (b) These kinetic equations are used to calculate the set of reagent amino- and keto-acid concentrations that all yield a selected fraction of the theoretical maximum enzyme velocity.

Computer simulation of the metabolism of guinea pig brain slices, and how they differ from the intact brain.

A computer model of the metabolism of glutamate, glutamine, gamma-aminobutyrate and the Krebs cycle in guinea pig cortex slices has been constructed in terms of 98 reactions among 38 unlabeled species. Fitting the data from slices required the addition of a third small compartment to previous 2-compartment models based on whole brain experiments. This third compartment corresponds to the tissue damaged during the slicing process, and dominates the metabolism of 14C-labeled substrates at early times.

Biochemistry and genetics of Klebsiella pneumoniae mutant strains unable to fix N2.

Selected mutant strains of Klebsiella pneumoniae that are unable to fix nitrogen have been characterized according to nitrogenase component activity as well as antigenic cross-reacting material. The lesions in these strains have been mapped by transduction, and the results indicate that there are at least five genes specifically responsible for nitrogen fixation in vivo. Besides genes that specify the structure of the two nitrogenase components, there is a gene for a factor that is required for component I activity and a gene that codes for a factor possibly involved in electron transport to component II.

Simulation of the pentose cycle in lactating rat mammary gland.

A computer model representing the pentose cycle, the tricarboxylic acid cycle and glycolysis in slices of lactating rat mammary glands has been constructed. This model is based primarily on the studies, with radioactive chemicals, of Abraham & Chaikoff (1959) [although some of the discrepant data of Katz & Wals (1972) could be accommodated by changing one enzyme activity]. Data obtained by using [1-(14)C]-, [6-(14)C]- and [3,4-(14)C]-glucose were simulated, as well as data obtained by using unlabelled glucose (for which some new experimental data are presented).

A simulation study of brain compartments. Metabolism of glutamate and related substances in mouse brain.

A computer model of the metabolism of glutamate, glutamine, gamma-aminobutyrate, and the tricarboxylic acid cycle in mouse brain has been constructed in terms of 39 reactions among 19 substances or groups of substances (permitting manipulation of 30 independent variables). The model is divided into two compartments, in conformity with previous models based on indirect evidence, and it is found that this compartmentation is indeed the same as that indicated directly with specifically (14)C-labelled acetate and glucose. The movement of materials between the large and small compartments has been studied; glutamine appears to flow from the small to the large compartment, gamma-aminobutyrate in the reverse direction.