The cDNA cloning and molecular evolution of reptile and pigeon lactate dehydrogenase isozymes

The cDNAs encoding lactate dehydrogenase isozymes LDH-A (muscle) and LDH-B (heart) from alligator and turtle and LDH-A, LDH-B, and LDH-C (testis) from pigeon were cloned and sequenced. The evolutionary relationships among vertebrate LDH isozymes were analyzed. Contrary to the traditional belief that the turtle lineage branched off before the divergence between the lizard/alligator and bird lineages, the turtle lineage was found to be clustered with either the alligator lineage or the alligator-bird clade, while the lizard lineage was found to have branched off before the divergence between the alligator/turtle and bird lineages. The pigeon testicular LDH-C isozyme was evidently duplicated from LDH-B (heart), so it is not orthologous to the mammalian testicular LDH-C isozymes.      

Purification and Characterization of Yeast β-Glucosidases

Constitutive beta-glucosidases from Saccharomyces fragilis (Y-18) and S. dobzhanskii (Y-19) precipitated at the same concentration of ammonium sulfate. The partially purified enzymes had similar activation energies, molecular weights, affinities for certain natural and synthetic beta-glucosides, and optimal pH values for substrate hydrolysis, and they were stable over approximately the same pH range. The enzymes, however, could be clearly distinguished by other criteria. Affinities of the synthetic, sulfur-containing beta-glucosides for Y-18 enzyme were many times greater than for Y-19 enzyme. The latter enzyme was more resistant to heat. The two enzymes eluted from diethylaminoethyl cellulose at different concentrations of sodium chloride. In precipitin tests, homologous enzyme-antisera systems were highly specific. The beta-glucosidase synthesized by a hybrid, S. fragilis x S. dobzhanskii (Y-42), was unique. Characterization of this enzyme produced values which were intermediate to those for the enzymes from the parental yeast strains. Heat-inactivation slopes and Lineweaver-Burk plots for the Y-42 enzyme were anomalous. It is suggested that hydrolytic activity in Y-42 preparations is due to a spectrum of hybrid enzyme molecules composed of varying amounts of two distinct polypeptides. It is further suggested that these polypeptides may be identical to those synthesized by the parental Y-18 and Y-19 yeast strains.     

Production of neosolaniol monoacetate by an undescribedFusarium species resemblingF camptoceras

Cultures of 12 South African isolates of an undescribedFusarium species resembling but distinct fromF camptoceras were analysed for the presence of diacetoxyscirpenol (DAS), neosolaniol monoacetate (NMA), and T-2 toxin, by capillary gas chromatography utilizing electron capture detection. No DAS or T-2 toxin could be detected in any of the cultures of the isolates. NMA was, however, detected in 10 of the 12 isolates at levels ranging from 310 to 2060 ng/g. The method used, was primarily developed for the determination of DAS and T-2 toxin in fungal cultures and grain samples but was found to be suitable for the coextraction of NMA at an average recovery of 80.8%, with a detection limit in the order of 100 ng/g. Supportive evidence for the presence of the NMA was obtained by capillary gas chromatography / mass spectrometry. Regarded as a relatively rare trichothecene, NMA has never been reported to occur naturally and has previously been shown to be produced by only a fewFusarium strains.     

Analyses of relative protein content and distribution of histones in euchromatic and heterochromatic fractions.

Euchromatic and heterochromatic fractions obtained by autodigestion of mouse TLT (taper liver tumour) hepatoma chromatin (Paul, I. J & Duerksen, J. D. (1976) Arch. Biochem. Biophys. 174, 491-505) were analyzed for relative protein content and histone content. With one exception, all fractions had the same DNA to protein ratio. Similarly, the total histone to DNA ratio was also constant in all fractions. In addition, the relative contents of the major histones, H1, (H2A + H2B + H3), and H4, were also constant in all fractions.