Thiol and amino analogues as alternate substrates for glycerokinase from Candida mycoderma.

The kinetic and catalytic mechanism of glycerokinase from Candida mycoderma was examined with thiol and amino analogues of glycerol and with MgAMPPCP, an analogue of MgATP. (S)-1-Aminopropanediol was phosphorylated on nitrogen (Vmax 0.4% that of glycerol) while the R enantiomer was phosphorylated on oxygen (Vmax 0.

Structure of oxobis(phenolato)[tris(3,5-dimethyl-1-pyrazolyl)-hydroborato]molybdenum (V).

C27H32BMoN6O3, Mr = 595.34, monoclinic, P2(1)/n, a = 16.376 (6), b = 10.

Triamminemonoaquocobalt(III) complexes of pyrophosphate and adenosine diphosphate (ADP).

Cobalt(III)H2O(NH3)3 pyrophosphate has been shown by proton and 31P nuclear magnetic resonance (NMR) to be a facial bidentate complex. Cobalt(III)H2O(NH3)3 adenosine diphosphate has been resolved into lambda and delta isomers by chromatography on cycloheptaamylose. Both the lambda and delta forms are a pair of isomers that are not separated by cycloheptaamylose, reverse phase high-pressure liquid chromatography (HPLC), or cation exchange chromatography.

Steady-state kinetic studies of the metal ion-dependent decarboxylation of oxalacetate catalyzed by pyruvate kinase.

Steady-state kinetic studies with differing divalent metals ions have been carried out on the pyruvate kinase-catalyzed, divalent cation-dependent decarboxylation of oxalacetate to probe the role of the divalent metal ion in this reaction. With either Mn2+ or Co2+, initial velocity patterns show that the divalent metal ion is bound to the enzyme in a rapid equilibrium prior to the addition of oxalacetate. Further, there is no change in the initial velocity patterns or the kinetic parameters in the presence or absence of K+, indicating that K+ is not required for oxalacetate decarboxylation.

Enzymatic synthesis and inhibitory characteristics of tartronate semialdehyde phosphate.

The immediate product of the pyruvate kinase catalyzed phosphorylation of beta-hydroxypyruvate is the enol of tartronate semialdehyde phosphate (TSP). The reaction has the same pH profile as that for the phosphorylation of pyruvate with pK's of 8.2 and 9.

Use of primary deuterium and 15N isotope effects to deduce the relative rates of steps in the mechanisms of alanine and glutamate dehydrogenases.

We have used deuterium and 15N isotope effects to study the relative rates of the steps in the mechanisms of alanine and glutamate dehydrogenases. The proposed chemical mechanisms for these enzymes involve carbinolamine formation, imine formation, and reduction of the imine to the amino acid [Grimshaw, C.E.

Carbon-13 and deuterium isotope effects on the catalytic reactions of biotin carboxylase.

13C and 2H kinetic isotope effects have been used to investigate the mechanism of enzymic biotin carboxylation. D(V/K) is 0.50 in 80% D2O at pD 8.

Catalytic mechanism of biotin carboxylase: steady-state kinetic investigations.

Biotin carboxylase was purified from Escherichia coli by a new procedure, and its steady-state kinetic parameters were examined. MgATP and bicarbonate add to the enzyme randomly, followed by addition of biotin. Both bicarbonate and MgATP add in rapid equilibrium.

Isotope effect studies of the chemical mechanism of pig heart NADP isocitrate dehydrogenase.

The catalytic mechanism of porcine heart NADP isocitrate dehydrogenase has been investigated by use of the variation of deuterium and 13C kinetic isotope effects with pH. The observed 13C isotope effect on V/K for isocitrate increases from 1.0028 at neutral pH to a limiting value of 1.

Isotope effect studies of chicken liver NADP malic enzyme: role of the metal ion and viscosity dependence.

The role of the metal ion in the oxidative decarboxylation of malate by chicken liver NADP malic enzyme and details of the reaction mechanism have been investigated by 13C isotope effects. With saturating NADP and the indicated metal ion at a total concentration 10-fold higher than its Km, the following primary 13C kinetic isotope effects at C4 of malate [13(V/Kmal)] were observed at pH 8.0: Mg2+, 1.

Large benign virilizing adrenal adenoma.

The young woman described sought evaluation for infertility and was found to have virilization due to a large left adrenal tumor. Further endocrine studies confirmed a syndrome of pure virilization with normal glucocorticoid function. Resection of this apparently benign tumor resulted in regression of virilization, as well as pregnancy.

Kinetics and mechanism of benzoylformate decarboxylase using 13C and solvent deuterium isotope effects on benzoylformate and benzoylformate analogues.

Benzoylformate decarboxylase (benzoylformate carboxy-lyase, BFD; EC 4.1.1.

Carbon-13 isotope effects on reactions involving carbamate and carbamoyl phosphate.

Several 13C isotope effects of relevance to reactions involving carbamate and carbamoyl phosphate have been determined. The fractionation factor of carbamate relative to aqueous CO2 is 1.011; the equilibrium isotope effect on the reaction catalyzed by carbamate kinase is 0.

2-Keto-3-fluoroglutarate: a useful mechanistic probe of 2-keto-glutarate-dependent enzyme systems.

2-Keto-3-fluoroglutaric acid prepared by acid hydrolysis of its diethyl ester is stable, as the free acid in aqueous solution at pH 2, and can be stored at -20 degrees C for several years. Both enantiomers are reduced by NADH in the presence of glutamate dehydrogenase (EC 1.4.

Evidence from nitrogen-15 and solvent deuterium isotope effects on the chemical mechanism of adenosine deaminase.

We have determined 15N isotope effects and solvent deuterium isotope effects for adenosine deaminase using both adenosine and the slow alternate substrate 7,8-dihydro-8-oxoadenosine. With adenosine, 15N isotope effects were 1.0040 in H2O and 1.

Effect of the presence of a reversible inhibitor on the time course of slow-binding inhibition.

The half-time for the initial burst seen when a slow-binding inhibitor is present in an enzyme assay decreases from 0.693/k4 to 0.693/(k3 + k4) as the concentration of the slow-binding inhibitor is increased from zero to infinity (k3 and k4 are forward and reverse rate constants for the isomerization causing the slow-binding behavior).

Decarboxylation of oxalacetate by pyruvate carboxylase.

The decarboxylation of oxalacetate by pyruvate carboxylase in the absence of ADP and Pi is stimulated 400-fold by the presence of oxamate, which is an inhibitory analogue of pyruvate. The observation of substrate inhibition when either oxamate or oxalacetate is varied at a fixed concentration of the other indicates that both molecules bind at the same site on the enzyme. The pH profiles for this reaction show no evidence of the involvement of an enzymic acid-base catalyst, suggesting that the proton and CO2 units may be exchanged directly between the reactants (although CO2 sequestered in the active site may be an intermediate in the process).

Carbon-13 and deuterium isotope effects on oxalacetate decarboxylation by pyruvate carboxylase.

Deuterium and 13C isotope effects for the enzymic decarboxylation of oxalacetate showed that both deuterium- and 13C-sensitive steps in the reaction are partially rate limiting. A normal alpha-secondary effect of 1.2 per deuterium was calculated for the reaction in which pyruvate-d3 was the substrate, suggesting that the enolate of pyruvate was an intermediate in the reaction.

Subglottic hemangiomas in infants.

Subglottic hemangioma, a lesion absent at birth and developing in the first few months of life, may present as an acute airway obstruction. Definitive diagnosis may be delayed or confused with other conditions. Recent experience with infants presenting with subglottic hemangioma lead to the proposal of delayed laser surgical intervention until age nine months, at which time natural involution begins.

The longevity of sterilized aortic valve homografts 1966-1972.

Between 1966 and 1972 seventy-two adult patients underwent aortic valve replacement with unstented aortic valve homografts prepared by chemical beta-propiolactone sterilization and storage. There were 5 hospital deaths and 6 foreign patients are lost to follow-up. Of the remaining 61, there have been 7 late deaths.