Turnover of hepatic phosphofructokinase in normal and diabetic rats. Role of insulin and peptide stabilizing factor.

Earlier work demonstrated that the activity of liver phosphofructokinase (PFK-L2) and immunoreactive PFK-L2 were decreased in diabetic rats and increased to normal or super-normal amounts following insulin treatment (Dunaway, G.A., and Weber, G., (1974) Arch. Biochem. Biophys. 162, 629-637). This report indicates that the decrease in levels of PFK-L2 in diabetic rats is a result of an accelerated degradation rate while the synthetic rate remains nearly normal. Following insulin treatment, the rate of PFK-L2 synthesis is enhanced 2-fold, whereas the rate of degradation appears to be greatly diminished. An inverse relationship is shown to exist between the PFK-L2 levels and the rates of PFK-L2 degradation, suggesting that the levels of PFK-L2 are primarily regulated by degradation rate. In addition, the levels of the PFK-L2 peptide stabilizing factor are inversely proportional to rates of PFK-L2 degradation. These results indicate that insulin mediates the rate of degradation of PFK-L2 by controlling the level of the peptide stabilizing factor.     

Tau, sigma, and delta. A family of repeated elements in yeast

We report here the isolation and structure of a new repeated DNA element, tau. This element, from Saccharomyces cerevisiae, is 371 base pairs long and is flanked on either end by the same invertedly repeated sequence found at the ends of some Ty and sigma elements in yeast, copia elements in Drosophila and spleen necrosis virus. The tau inverted repeats are themselves flanked by a 5-base pair directly repeated genomic sequence that is present only once in a cognate tau-allele. These structural characteristics, the presence of multiple copies of tau in the genome, and the isolation of tau+ and tau- allelic pairs suggest that tau may be capable of transposition either alone or in association with some larger element. Detailed sequence analysis of the tau, sigma, and delta elements revealed that all three contain significant regions of homology, suggesting that they are probably members of a single family derived from a common progenitor.     

A single succinic semialdehyde dehydrogenase is involved in 4-hydroxyphenylacetate and 4-aminobutyrate catabolism in Klebsiella pneumoniae M5a1

Abstract Klebsiella pneumoniae M5a1 grows readily on two compounds, 4-hydroxyphenylacetate and 4-aminobutyrate, whose catabolism produces succinic semialdehyde. A single succinic semialdehyde dehydrogenase was detected, native molecular weight 52000, that has NAD as the preferred cofactor and is induced by succinic semialdehyde functions in the oxidation of succinic semialdehyde during growth on both 4-hydroxyphenyl-acetate and 4-aminobutyrate. This contrasts with the situation for Escherichia coli and Pseudomonas putida where two distinct forms of succinic semialdehyde dehydrogenase have been observed.     

N-caffeoyl-4-amino-n-butyric acid, a new flower-specific metabolite in cultured tobacco cells and tobacco plants

PUT cells were selected from the XD line of cultured tobacco cells (Nicotiana tabacum L. cv. Xanthi-nc) for the ability to utilize putrescine as sole nitrogen source. Previous work had indicated that hydroxycinnamoylputrescines (principally caffeoylputrescine) and 4-amino-n-butyric acid (GABA) are obligatory intermediates in the assimilation of putrescine by PUT cells. The apparent absence in these cells of diamine or polyamine oxidase and pyrroline dehydrogenase, enzymes which catalyze putrescine oxidation in some plant species, led us to propose the following pathway for putrescine oxidation in PUT cells: putrescine----hydroxycinnamoylputrescine----hydroxycinnamoyl - 4-aminobutyraldehyde----hydroxycinnamoyl-GABA----GABA. We tested the hypothesis by looking for the predicted compound, caffeoyl-GABA. A chemical synthesis was developed, and chromatographic and mass spectroscopic procedures were devised for identifying the compound in extracts of cells and plant tissues. Caffeoyl-GABA was found in extracts of PUT cells in micromolar concentrations but was not present in XD cells. Thus, its occurrence in PUT cells appears to be a direct result of selection for the ability to catabolize putrescine. Caffeoyl-GABA has the same distribution in tobacco plants as caffeoylputrescine, i.e. flower buds greater than open flowers greater than floral leaves, green fruit; absent in vegetative tissues.     

The mannoprotein of Saccharomyces cerevisiae is an effective bioemulsifier

The mannoprotein which is a major component of the cell wall of Saccharomyces cerevisiae is an effective bioemulsifier. Mannoprotein emulsifier was extracted in a high yield from whole cells of fresh bakers' yeast by two methods, by autoclaving in neutral citrate buffer and by digestion with Zymolase (Miles Laboratories; Toronto, Ontario, Canada), a beta-1,3-glucanase. Heat-extracted emulsifier was purified by ultrafiltration and contained approximately 44% carbohydrate (mannose) and 17% protein. Treatment of the emulsifier with protease eliminated emulsification. Kerosene-in-water emulsions were stabilized over a broad range of conditions, from pH 2 to 11, with up to 5% sodium chloride or up to 50% ethanol in the aqueous phase. In the presence of a low concentration of various solutes, emulsions were stable to three cycles of freezing and thawing. An emulsifying agent was extracted from each species or strain of yeast tested, including 13 species of genera other than Saccharomyces. Spent yeast from the manufacture of beer and wine was demonstrated to be a possible source for the large-scale production of this bioemulsifier.     

Trichomoniasis in free-living goshawks (Accipiter gentilis gentilis) from Great Britain

The goshawk Accipiter gentilis has recently been reintroduced into parts of Great Britain. During the course of a study of one population, lesions of stomatitis were observed in 14 young from five broods and all the affected birds died. Postmortem examination of three birds revealed live Trichomonas gallinae in exudate from one, and histological findings consistent with a diagnosis of trichomoniasis were made in this and one other bird. It is suggested that trichomoniasis may be a significant mortality factor in goshawks from Britain.