Enzyme variation in Plasmodium berghei and Plasmodium vinckei

A study of electrophoretic forms of a selection of enzymes has been made in strains of subspecies of the rodent malaria parasitesPlasmodium bergheiandP. vinckei. Considerable electrophoretic variation of these enzymes occurred among the strains studied. On the basis of the results it was possible to identify groups of parasites within each species. While generally substantiating the classical taxonomy the identification of groups provided further information on the relationships between the subspecies.

Respiration and protein synthesis in Escherichia coli membrane-envelope fragments. VI. Solubilization and characterization of the electron transport chain

Membranes obtained from Escherichia coli have been solubilized with deoxycholate. The solubilized dehydrogenases and cytochromes are not sedimented at 105,000 g. These components readily penetrate the "included space" of Sepharose 4B (Pharmacia Fine Chemicals Inc., Uppsala, Sweden) and polyacrylamide gels and have been fractionated on the basis of molecular size. Solubilization destroys nicotinamide adenine dinucleotide, reduced form (NADH) oxidase and D-lactate oxidase activities, but leaves an appreciable part of the original succinoxidase activity intact. Evidence for a succinate dehydrogenase-cytochrome b(1) complex is given. Menadione added to the solubilized preparation does not elicit NADH oxidase activity nor stimulate the existing succinoxidase activity, but does provoke an active D-lactate oxidase activity. This D-lactate oxidase activity, however, does not use cytochromes and is not sensitive to cyanide.

Malate dehydrogenase in maize endosperm: the intracellular location and characterization of the two major particulate isozymes

Multiple molecular forms of malate dehydrogenase (MDH) were detected in several tissues of maize using polyacrylamide gel electrophoresis. An investigation of MDH in 14-day-old endosperm tissue revealed that the two major isozymes were associated with particulate cell fractions, the mitochondria and glyoxysomes. Preparations of these two particulate isozymes, designated m-MDH and g-MDH, were obtained by anion-exchange chromatography and several physical and kinetic parameters were measured. Both isozymes had approximately the same Stokes radius (34 Å) but were catalytically distinct. Differences were found in their relative rates of reaction with NAD and two of its analogues (thionicotinamide-NAD and acetylpyridine-NAD) as well as in changes of Km (oxalacetate) with pH. The possible physiological roles of these two isozymes are discussed.

Regulation of the two "malic" enzymes in Neurospora crassa

Two NADP-specific "malic" enzymes have been found to be present in Neurospora crassa. They have different pH optima and are influenced differently by some metabolites and inhibitors. The pH 8.0 "malic" enzyme appears during the early stages of growth and is inhibited by fructose 1,6-diphosphate while the pH 10.0 "malic" enzyme appears during the later stages of growth and is inhibited by aspartate. Both enzymes are repressed by acetate and pyruvate and their activities are inhibited by glyoxylate and oxaloacetate. The metabolic function of the enzymes is discussed.

A study of spontaneous mutation rates at ten loci detectable by starch gel electrophoresis in Drosophila melanogaster

Spontaneous mutation rates at ten allozyme loci on chromosomes II and III of Drosophila melanogaster were studied. Over the three and a half years study, one alpha-GPD mutation and two different IDH mutations were obtained. The alpha-GPD mutation was inherited in the Mendelian fashion, as expected. The two IDH mutations were peculiar in that the band of new types appeared only in females. In males, only the original bands were stained, and the positions where mutant alleles' bands should be present were blank. Both IDH mutant homozygotes appeared as null allele homozygotes, while in females clear-cut single bands were present.-The rates of spontaneous mutation varied greatly. Eight loci studied (MDH, ADH, EST-6, APH, EST-C, ODH, XDH, AO) did not give any germ-line mutation. The average germ-line mutation rate over all ten loci was estimated at 4.5 x 10(-6). This rate is considerably smaller than that for sex-linked recessive visible mutations (Muller, Valencia and Valencia 1950), but it is somewhat less than autosomal recessive visible mutations (Glass and Ritterhoff 1956).