Characterization of a Fatty Acid Synthetase from \u3ci\u3eCorynebacterium diphtheriae\u3c/i\u3e

A fatty acid synthetase from Corynebacterium diphtheriae has been purified to a specific activity of 450 nmoles of malonyl coenzyme A incorporated per min per mg. The enzyme is optimally active in 0.5 M phosphate buffer. C. diphtheriae appears to be the most primitive organism having a multienzyme complex for fatty acid synthesis

Palmityl Coenzyme A Inhibition of Fatty Acid Synthesis

The effects of acyl-CoA derivatives (C8 to C20) on the activity of the fatty acid synthetases from yeast and Corynebacterium diphtheriae have been examined. Both enzyme systems are inhibited by the longer chain acyl thioesters (C16 to C20) and protected against this inhibition by bovine serum albumin (BSA). Identical relief from acyl-CoA inhibition is provided by the 6-0-methylglucose-containing lipopolysaccharide (MGLP), from Mycobacterium phlei. It is shown that MGLP forms a stable complex with palmitylCoA. This interaction accounts for the BSA-like effects of the polysaccharide. BSA and MGLP have two further effects on the fatty acid synthetases under study, also attributable to complex formation with palmityl-CoA. They stimulate the rate of over-all synthesis from acetyl-CoA and malonyl-CoAt and they cause a shift of the fatty acid pattern towards products of shorter chain length. The observed effects are discussed in terms of the regulation of fatty acid synthesis both with respect to rate and product composition. It is concluded that in the two microbial enzyme systems negative feedback inhibition and its relief are important control mechanisms

The Structure of an Ornithine-containing Lipid from \u3ci\u3eThiobacillus thiooxidans\u3c/i\u3e

The structure of an ornithine-containing lipid from Thio-bacillus thiooxidans has been elucidated. Methanolysis of the lipid released methyl cis-ll,lZ-methylene-Z-hydroxyoctadecanoate. Acid hydrolysis of the residue yielded ornithine and a mixture of fatty acids, the major components of which were 3-hydroxyhexadecanoic and 2-hexadecenoic acids. Identification of the 3-hydroxy fatty acid was based on the thin layer chromatographic mobilities of the acid, its methyl ester, the methyl ether, and acetate derivatives of its methyl ester, on the equivalent chain lengths of the derivatives of the acid and the acid obtained by oxidation of the natural acid with permanganate, and on mass spectral studies. Similar techniques were used for the identification of 2-hexadecenoic acid. The minor fatty acids and the 2-hexadecenoic acid were found to be degradation products of the 3-hydroxy acid

Characterization of a Fatty Acid Synthetase from \u3ci\u3eCorynebacterium diphtheriae\u3c/i\u3e

A fatty acid synthetase from Corynebacterium diphtheriae has been purified to a specific activity of 450 nmoles of malonyl coenzyme A incorporated per min per mg. The enzyme is optimally active in 0.5 M phosphate buffer. C. diphtheriae appears to be the most primitive organism having a multienzyme complex for fatty acid synthesis

The Binding of Host-Selective Toxin Analogs to Mitochondria from Normal and \u27Texas\u27 Male Sterile Cytoplasm Maize

Tritium-labeled toxin analogs were prepared by reduction with NaB3H4 of either the toxin from Helminthosporium maydis race T or a toxin component from Phyllosticta maydis. These reduced analogs had high radiochemical specific activities, high biological activities, and plant specificities identical to the native toxins. A filtration assay was developed to test the binding of these labeled analogs to isolated- mitochondria. Binding was not energy dependent nor was there measurable matrical uptake. The analogs were shown to be lipophilic, a characteristic which gave rise to considerable nondisplaceable binding. Under conditions limiting nondisplaceable binding, -the displaceable binding was shown to be linear with respect to toxin concentration and unsaturable. No significant differences were observed in the binding characteristics between the mitochondria from normal and male-sterile (Texas) cytoplasm maize. The findings suggest that, at physiologically relevant concentrations, these toxin analogs permeate the membranes of susceptible and resistant mitochondria alike. The lack of demonstrable specific binding does not rule out the involvement of a classical receptor site but does indicate that other kinds of molecular interactions may be involved in the mechanisms for toxicity and specificity

Palmityl Coenzyme A Inhibition of Fatty Acid Synthesis

The effects of acyl-CoA derivatives (C8 to C20) on the activity of the fatty acid synthetases from yeast and Corynebacterium diphtheriae have been examined. Both enzyme systems are inhibited by the longer chain acyl thioesters (C16 to C20) and protected against this inhibition by bovine serum albumin (BSA). Identical relief from acyl-CoA inhibition is provided by the 6-0-methylglucose-containing lipopolysaccharide (MGLP), from Mycobacterium phlei. It is shown that MGLP forms a stable complex with palmitylCoA. This interaction accounts for the BSA-like effects of the polysaccharide. BSA and MGLP have two further effects on the fatty acid synthetases under study, also attributable to complex formation with palmityl-CoA. They stimulate the rate of over-all synthesis from acetyl-CoA and malonyl-CoAt and they cause a shift of the fatty acid pattern towards products of shorter chain length. The observed effects are discussed in terms of the regulation of fatty acid synthesis both with respect to rate and product composition. It is concluded that in the two microbial enzyme systems negative feedback inhibition and its relief are important control mechanisms