Chemically induced porphyria: increased microsomal heme turnover after treatment with allylisopropylacetamide

Excessive induction of delta-aminolevulinic acid synthetase in rats after treatment with porphyria-inducing chemicals, such as allylisopropylacetamide, is accompanied by a decrease in microsomal heme and cytochrome P450 concentrations. Measurement of the radioactive decay after labeling of the heme moiety of submicrosomal particles shows increased breakdown of heme in rats treated with allylisopropylacetamide. The effects of allylisopropylacetamide on heme synthesis and heme turnover may be interrelated

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.

Hemin-deficient mutants of Salmonella typhimurium

Nine hemin-deficient mutants of Salmonella typhimurium LT2 were isolated as neomycin-resistant colonies. Five of these mutants could be stimulated by Delta-aminolevulinic acid (Delta-ALA), thus representing hemA mutants. Since S. typhimurium LT2 is not able to incorporate hemin, the identification of the mutants not stimulated by Delta-ALA was made on the basis of the simultaneous loss of catalase activity and cytochromes. The hemA gene was mapped by conjugation in the trp region, probably in the order purB-pyrD-hemA-trp; the episome FT(71)trp does not carry the hemA gene. Transductional intercrosses by phage P22 indicate that hemA 11, 12, 13, and 37 are at very closely linked sites, whereas hemA14 is at a more distant site in the same or an adjacent gene. No joint transduction was detected between hemA and trp or pyrF. The loci affected in the other hemin-deficient mutants were linked in conjugation to the pro(+) marker (frequency of linkage, 88 to 97%), but cotransduction of the two markers could not be obtained. The episome F lac hem purE, which originates from Escherichia coli K-12, could complement these hemin-deficient mutants of S. typhimurium LT2. As a result, the sequence of the markers on the chromosome of S. typhimurium LT2 is probably pro heme purE, analogous to the sequence found in E. coli K-12. Thus, the chromosome of S. typhimurium also possesses two hem regions, with a location similar to that described in E. coli K-12.

A kinetic study of the effects of delta-aminolevulinic acid upon the synthesis of embryonic and fetal hemoglobins in the blood islands of the developing chick blastodisc

Chick blastodiscs contained and synthesized a functional (embryonic) hemoglobin as early as the stage of the definitive primitive streak. The rate of hemoglobin synthesis in ovo rose dramatically at about the stage of the 3-somite embryo.Embryos explanted onto solid media at the 3-somite stage of development continued to synthesize hemoglobin in vitro for at least 12 h. The rate of synthesis rose markedly at the 6-somite stage of development, coincident with the onset of rapid synthesis of fetal hemoglobin. A supplement of exogenous aminolevulinic acid markedly stimulated the synthesis of hemoglobin before the 6-somite stage of development, but had little or no effect thereafter. These responses were obtained on both minimal and rich media. Levels of hemoglobin formed were characteristic of the final stages of development attained, regardless of initial stage of development, medium used, or time of incubation required to attain the final level of development.A new regulatory process resulting in elimination of a requirement for continuous presence of egg homogenate for maximal rates of hemoglobin was revealed. This took place between the 6- and 8-somite stages of development at the time of onset of rapid synthesis of fetal hemoglobin.

Induction of dimorphism in the basidiomycete Lenzites saepiaria

Sugars can serve as the germinant for basidiospores of the wood-rotting fungus Lenzites saepiaria. Hexoses sterilized by autoclaving were better germinants than hexoses that were sterilized by filtration. The degradation products in heated hexose which were responsible for the stimulation of germination were levulinic and formic acid. Another product of hexose degradation, hydroxymethyl furfural, had a marked effect on outgrowth of L. saepiaria basidiospores and on the development of mycelia. Basidiospores that germinated in the presence of hydroxymethyl furfural yielded large rounded bodies that, in some cases, developed as a chain of yeastlike cells. Addition of hydroxymethyl furfural to developing mycelia resulted in the production of chains of round yeastlike structures. Similar results were obtained by treating basidiospores or mycelia with phenethyl alcohol.