Regulatory properties of a fructose 1,6-bisphosphatase from the cyanobacterium Anacystis nidulans.

A fructose 1,6-bisphosphatase (EC 3.1.3.11) (FBPase) was purified over 100-fold from Anacystis nidulans. At variance with a previous report (R. H. Bishop, Arch. Biochem. Biophys. 196:295-300, 1979), the regulatory properties of the enzyme were found to be like those of chloroplast enzymes rather than intermediate between chloroplast (photosynthetic) and heterotrophic FBPases. The pH optimum of Anacystis FBPase was between 8.0 and 8.5 and shifted to lower values with increasing Mg2+ concentration. Under the experimental conditions used by Bishop, we found the saturation curve of the enzyme to be sigmoidal for Mg2+ ions and hyperbolic for fructose 1,6-bisphosphate. The half-maximal velocity of the Anacystis FBPase was reached at concentrations of 5 mM MgCl2 and 0.06 mM fructose 1,6-bisphosphate. AMP did not inhibit the enzyme. The activity of the FBPase was found to be under a delicate control of oxidizing and reducing conditions. Oxidants like O2, H2O2, oxidized glutathione, and dehydroascorbic acid decreased the enzyme activity, whereas reductants like dithiothreitol and reduced glutathione increased it. The oxido-reductive modulation of FBPase proved to be reversible. Reduced glutathione stimulated the enzyme activity at physiological concentrations (1 to 10 mM).l The reduced glutathione-induced activation was higher at pH 8.0 than at pH 7.0.     

An aggregation attractant for the sugar-beet weevil, Bothynoderes punctiventris

During our screening studies, attractiveness of a ternary mixture of synthetic Grandlure I [racemic cis‐1‐methyl‐2‐(1‐methylenethenyl)‐cyclobutane ethanol], Grandlure II [(Z)‐2‐(3,3‐dimethyl)cyclohexylidene ethanol], and Grandlure III–IV [(Z)‐ and (E)‐2‐ochtodenal; (Z)‐ and (E)‐(3,3‐dimethyl)cyclohexylidene acetaldehyde] for the sugar‐beet weevil, Bothynoderes punctiventris Germar (Coleoptera: Curculionidae), was observed in field‐trapping tests at several sites in Hungary and Serbia. The mixture attracted both males and females. Later tests revealed that of the components in the ternary mixture, only Grandlure III–IV were responsible for attraction, and the addition of Grandlures I or II in varying percentages had no influence on trap captures. Traps baited with 50–50 000 µg of Grandlure III–IV on rubber or polyethylene dispensers yielded high catches of weevils. When testing synthetic samples enriched in the respective geometrical isomer, Grandlure IV had a tendency of catching more weevils, but differences were not significant from lower catches by a 1:1 Z:E blend or Grandlure III. In gas chromatography–flame ionization detection/electroantennographic detection studies, antennae of both female and male weevils were more responsive to the (E)‐ than to the (Z)‐isomer suggesting a more important role for Grandlure IV. Efforts to verify the presence of Grandlure III or IV in volatiles collected from either sex of live sugar‐beet weevils or body washings with pentane remained inconclusive. Traps baited with Grandlure III–IV can now be used as sensitive and powerful trapping tools in the control of the sugar‐beet weevil.     

Effects of plumbous ion on guanine metabolism.

The enzyme guanine aminohydrolase (guanase) is inhibited by low levels of Pb2+. The inhibition is noncompetitive and the Ki is 3.0 X 10(-6) M. The only other heavy metals that are inhibitory at low concentrations are Ag+, which is 36% more, and Hg2+, which is about 50% less inhibitory than Pb2+. The inhibition of guanase by Pb2+ and Hg2+ is synergistic and the inhibition of the enzyme was readily reversed by EDTA. The relationship of these studies with guanase and to the etiology and treatment of saturnine gout, which appears in humans suffering from lead poisoning, is discussed.     

Queuine metabolism and cadmium toxicity in Drosophila melanogaster

Queuine can replace guanine in the anticodon of certain tRNAs and is a hypermodified guanine derivative that can be synthesized by bacteria but not by mice. The study demonstrates that Drosophila can incorporate dietary queuine into tRNA but cannot synthesize it de novo for this purpose. Since an earlier study had shown that dietary CdCl2 caused Drosophila to increase greatly the proportion of queuine-containing tRNA over non-queuine tRNA the ability of dietary queuine to counteract cadmium toxicity was evaluated. When queuine was present in the cadmium-containing medium more pupae matured into adults than when queuine was absent. Other studies had demonstrated that the transglycosylase enzyme, that catalyzes the replacement of guanine in the anticodon of tRNA by queuine, is present in Drosophila larvae but the tRNA is virtually devoid of queuine. This study shows that in the presence of dietary queuine the larval tRNA contains abundant amounts of queuine. Therefore, we postulate a significant role for bacteria in supplying queuine to Drosophila for its incorporation into tRNA and that the control of this process by Drosophila is passive, i.e. is not an essential feature in differentiation.