The effect of adenosine triphosphate on porphyrin excretion and on glycine metabolism in Rhodopseudomonas spheroides

Selective action of mycobacillin on the uptake of releasable cell materials by Aspergillus niger

The uptake of normally releasable (i.e. releasable in the absence of the antibiotic) cell constituents (namely lysine, proline, ATP, Pi, Na+, K+ and Ca2+) by sensitive cells of Aspergillus niger that occurs in the absence of mycobacillin is gradually enhanced with increase in concentration of the antibiotic until the uptake attains the maximum. With still higher concentrations the uptake decreases until it becomes the same as in the control without mycobacillin. Uptake follows saturation kinetics both in the absence and in the presence of the antibiotic. Mycobacillin significantly increases Vmax. for uptake with any effect on Km, Mycobacillin has no action on the uptake of non-releasable materials.

5-Aminolevulinic-acid synthetases from Rhodopseudomonas spheroides Y. Comparison of the purification and properties of enzymes extracted from bacteria grown in different iron concentrations

The two 5-aminolevulinic acid synthetases of Rhodopseudomonas spheroides Y. were extracted from cells grown in a 'low-iron' medium and purified. They have a specific activity 10-fold higher than the 'high-iron' enzymes described by us previously and have the same properties except that they do not contain any iron and have one free-SH group more per mole of enzyme (2 for E1; , for E2) Their inhibition by adenosine triphosphate and iron and their oxidation-reduction sensitivity are discussed in terms of light, oxygen and heme feed-back regulation of bacteriochlorophyll sunthesis.

Inactivation of glucose 6-phosphate dehydrogenase during germination and outgrowth of Bacillus cereus T endospores

The specific activity and total activity of glucose 6-phosphate dehydrogenase (EC 1.1.1.49) under conditions of complete cell breakage fall 10-20-fold during a 3h period of spore germination and outgrowth. The spores must germinate (lose refractility), but do not have to undergo outgrowth, for the loss of activity to occur. Glucose 6-phosphate dehydrogenase activity from cells as any stage of development is completely stable in extracts at 4 degrees C or 30 degrees C. All of the enzyme activity is found in a soluble (50000g supernatant) fraction and remains completely soluble throughout development. Soluble protein and total cellular protein remain constant for about 2h. Proteinases could not be detected or protein turnover demonstrated during the morphogenetic process. Phenylmethanesuophony fluoride and o-phenanthroline, inhibitors of proteolytic enzymes, do not prevent glucose 6-phosphate dehydrogenase inactivation when added to whole cells. Mixing experiments show no inhibitor of glucose 6-phosphate dehydrogenase to be present in late-stage cells. The enzyme is not excreted into the culture medium. Chloramphenicol and rifampicine immediately stop protein synthesis and development but not the inactivation of glucose 6-phosphate dehydrogenase. NaN3, 2,4-dinitrophenol or anaerobiosis immediately stop development and prevent the loss of enzyme activity. A requirement for metabolic energy is therefore probable. Extracts of spores pre-labelled with L[14C]leucine were made at various stages of morphogenesis and subjected to polyacrylamide-gel electrophoresis. Glucose 6-phosphate dehydrogenase, which was identified by a specific stain, did not lose 14C label, and therefore may not be degraded during the inactivation process.

Inactivation of isocitrate lyase during myxospore development in Myxococcus xanthus

The inactivation of isocitrate lyase which occurs during late stages of myxospore formation in Myxococcus xanthus was studied. Several findings are reported. (i) Protein synthesis is required over a specific time interval in order for isocitrate lyase inactivation to occur at a later time. (ii) Metabolic energy is required at all times during myxospore development if the inactivation is to occur. (iii) It was possible to inhibit protein turnover to a considerable extent without affecting the net loss in isocitrate lyase activity.

Studies on the porphobilinogen deaminase-uroporphyrinogen cosynthetase system of cultured soya-bean cells

1. Porphobilinogenase was isolated and purified from soya-bean callus tissue; its components, porphobilinogen deaminase and uroporphyrinogen isomerase, were separated and purified. 2. The purified porphobilinogenase was resolved into two bands on starch-gel electrophoresis. The molecular weights of porphobilinogenase, deaminase and isomerase fractions were determined by the gel-filtration method. Porphobilinogenase activity was affected by the presence of air; uroporphyrinogens were only formed under anaerobic conditions, although substrate consumption was the same in the absence of oxygen as in its presence. 3. pH-dependence of both porphobilinogenase and deaminase was the same and a sharp optimum at pH 7.2 was obtained. Isomerase was heat-labile, but the presence of ammonium ions or porphobilinogen afforded some protection against inactivation. The action of several compounds added to the system was studied. Cysteine, thioglycollate, ammonium ions and hydroxylamine inhibited porphobilinogenase; certain concentrations of sodium and magnesium salts enhanced activity; some dicarboxylic acids and 2-methoxy-5-nitrotropone inhibited the deaminase. 4. delta-Aminolaevulate and ethionine in the culture media stimulated porphyrin synthesis and increased porphobilinogenase activity, whereas iron deficiency resulted in porphyrin accumulation. 5. The development of chlorophyll and porphobilinogenase on illumination of dark-grown callus was followed. 6. A hypothetical scheme is suggested for the enzymic synthesis of uroporphyrinogens from porphobilinogen.