Canine erythrocyte pyruvate kinase. I. Properties of the normal enzyme

We have compared the kinetic, immunological, and electrophoretic properties of human and canine erythrocyte pyruvate kinase. Both enzymes are allosteric and subject to positive and negative regulation. The allosteric properties of the canine enzyme are more pronounced than those of the human enzyme; however, the properties of both enzymes are consistent with a regulatory function in the glycolytic pathway of their respective erythrocytes. Antiserum against the human enzyme gives precipitin lines of partial identity between the human and canine enzymes on immunodiffusion. The anti-human serum inactivates the enzymatic activity of both enzymes, although it is more effective against the human enzyme than the canine. The two enzymes have slightly different mobilities on starch gel electrophoresis. While we have demonstrated differences between erythrocyte pyruvate kinase from dogs and that from humans, we conclude that the enzymes are sufficiently similar in properties and function to allow use of the dog as a model for human erythrocyte pyruvate kinase deficiency.     

Evaluation of the teratogenic potential of a spray adhesive in hamsters.

Pregnant Syrian hamsters were placed in a 100-1 static inhalation chamber for 30 min twice daily on days 5-10 of gestation and exposed to 8.0 +/- 0.13, 11.6 +/- 0.11,or 13.23 +/- 0.49 g of "Foil Art Adhesive" and killed on day 14. Controls were placed in adjacent identical chambers but received no spray. The spray adhesive was toxic but not teratogenic at the doses administered. Maternal alopecia occurred upon exposure to the 2 highest dose levels, and 1 female died during exposure to the highest dose level. Fetal survival was not affected. Mean fetal weight was significantly decreased after exposure to all 3 dose levels, and delayed skeletal development occurred but was not dose related.     

A COMPARISON OF THE NEURAL REGULATION OF TYROSINE HYDROXYLASE ACTIVITY IN SYMPATHETIc GANGLIA OF ADULT MICE AND RATS

Surgical decentralization of the superior cervical ganglion (SCG) in rats and mice led to a fall in ganglionic tyrosine hydroxylase (T-OH) activity, and a loss of more than 90 per cent of the preganglionic neurone marker, choline acetyl transferase. T-OH activity was reduced by more than 50 per cent in mice SCG ten days after surgery, but fell by only 25 per cent in rat SCG after 21 days. The surgical procedure did not cause obvious histo-logical damage or loss of SCG cells in either species. Both T-OH and choline acetyl transferase activities in rat and mouse SCG recovered to normal three months after surgery. Reserpine treatment was more effective in rats in causing increased ganglionic T-OH activity than in mice. Neither decentralization nor reserpine treatment caused any changes in DOPA-decarboxylase or monoamine oxidase activities in rat SCG. These results demonstrate that T-OH activity in SCG is subject to trans-synaptic regulation in both rats and mice; this regulation does not apply to DOPA-decarboxylase or monoamine oxidase. Differences in basal sympathetic tone may explain the different results obtained in mice and rats.     

Serum esterase genetics in rats: Two new alleles at Es-2, a new esterase regulated by hormonal factors,and linkage of these loci to the Ag-C blood group locus

Two new alleles at the Es-2 locus are described which determine electrophoretic variants of serum esterases of rats. A new esterase protein is described which is detectable in sera of sexually mature females of the appropriate genotype. Evidence is presented for genetic linkage between the Ag-C blood group locus and Es-1, Es-2, and the locus controlling the sex-influenced protein. Since the Ea-1 blood group locus of mice is linked to four esterase loci, it is suggested that Ag-C is the rat homologue of the mouse Ea-1 locus.This work was supported by U.S.P.H.S. Grants AI-09275, CA-15146, and CA-10097.     

Characterization of Phosphoenolpyruvate Carboxykinase from Panicum maximum

Phosphoenolpyruvate carboxykinase, EC 4.1.1.32 (PEPCK), was purified 43-fold from the grass Panicum maximum. Michaelis constants (Km) were determined for the exchange reaction, the carboxylation reaction, and the decarboxylation reaction. The Km values for oxaloacetate and ATP in the decarboxylation reaction were found to be lower than the Km values for the substrates used in the exchange reaction and in the carboxylation reaction. Phosphoenolpyruvate carboxylase was not detectable in the purified PEPCK preparation.     

Malate Dehydrogenase and NAD Malic Enzyme in the Oxidation of Malate by Sweet Potato Mitochondria

Over a range of concentrations from less than 0.1 mm to more than 70 mm, sweet potato root mitochondria display a bimodal substrate saturation isotherm for malate. The high affinity portion of the isotherm has an apparent Km for malate of 0.85 mm and fits a rectangular hyperbolic function. The low affinity portion of the isotherm is sigmoid in character and gives an apparent S(0.5) of 40.6 mm and a Hill number of 3.7.Extracts of sweet potato mitochondria contain both malate dehydrogenase and NAD malic enzyme. The malate dehydrogenase, assayed in the forward direction at pH 7.2, shows typical Michaelis-Menten kinetics with a Km for malate of 0.38 mm. The NAD malic enzyme shows pronounced sigmoidicity in response to malate with a Hill number of 3.5 and an S(0.5) of 41.6 mm.On the basis of the normal kinetics, the Km, and the fact that oxaloacetate production from malate by mitochondria appears most active at low malate concentrations, the high affinity portion of the malate isotherm with mitochondria is attributed to malate dehydrogenase. The low affinity portion of the malate isotherm with mitochondria is thought, on the basis of the similarity of S(0.5) values, the Hill numbers, and the greater production of pyruvate from malate at high malate concentrations, to represent the activity of the NAD malic enzyme.     

DISC VARIANCE OF THE HARKEN MITRAL PROSTHESIS: THE CONTRIBUTION OF ASSOCIATED AORTIC REGURGITATION

Four cases of severe mitral regurgitation due to disc variance of the Harken disc prosthesis in the mitral position are described. The valve occluder actually escaped into the left atrium in two patients, and neither survived despite emergency valve replacement. In the other two, disc malfunction was identified by flouroscopy, the prosthesis was replaced, and both patients survived. All four patients had associated aortic regurgitation, which most likely contributed to erosion of the disc edges. It is suggested that patients with the Harken disc prosthesis undergo periodic evaluation to detect abnormal disc motion.