Inhibition and repression of homocitrate synthase by lysine in Penicillium chrysogenum

Homocitrate synthase in the first enzyme of the lysine biosynthetic pathway. It is feedback regulated by L-lysine. Lysine decreases the biosynthesis of penicillin (determined by the incorporation of [14C]valine into penicillin) by inhibiting and repressing homocitrate synthase, thereby depriving the cell of alpha-aminoadipic acid, a precursor of penicillin. Lysine feedback inhibited in vivo the biosynthesis and excretion of homocitrate by a lysine auxotroph, L2, blocked in the lysine pathway after homocitrate. Neither penicillin nor 6-aminopenicillanic acid exerted any effect at the homocitrate synthase level. The molecular mechanism of lysine feedback regulation in Penicillium chrysogenum involved both inhibition of homocitrate synthase activity and repression of its synthesis. In vitro studies indicated that L-lysine feedback inhibits and represses homocitrate synthase both in low- and high-penicillin-producing strains. Inhibition of homocitrate synthase activity by lysine was observed in cells in which protein synthesis was arrested with cycloheximide. Maximum homocitrate synthase activity in cultures of P. chrysogenum AS-P-78 was found at 48 h, coinciding with the phase of high rate of penicillin biosynthesis.     

The NADPH consumption regulates the NADPH-producing pathways (pentose phosphate cycle and malic enzyme) in rat adipocytes

The changes in the activity of the pentose phosphate cycle and the malic enzyme produced by the activation or inhibition of different NADPH-consuming pathways have been studied. The inhibition of the fatty acid synthesis by kynurenate produced a decrease in the flux through the pentose phosphate cycle and a diminution in the malic enzyme pathway. The incubation of the adipocytes in the presence of ter-butyl-hydroperoxide, a compound which is metabolized via a NADPH-consuming pathway, produced a big increase in the pentose phosphate cycle and the malic enzyme activities. The regulation of these NADPH-producing pathways by the NADPH/NADP ratio is discussed.     

Penicillin production by mutants ofPenicillium chrysogenum resistant to polyene macrolide antibiotics

Summary Polyene-resistant mutants ofPenicillium chrysogenum Wis. 54–1255 have been obtained by stepwise selection in increasing concentrations of polyene antibiotics. From the parent strain, sensitive to 10 g/ml of polyene antibiotics, mutants resistant to fungimycin (1.3 mg/ml), amphotericin B (0. 5 mg/ml), or nystatin (167 g//ml) were obtained. Their penicillin production is different from that of the parent strain and in particular some of the fungimycin-resistant mutants produce higher levels of penicillin.     

Studies on blood serum beta-N-acetylglucosaminidases from several mammalian species--separation of different enzyme forms.

1. The beta-N-acetylglucosaminidases studied from peripheral blood sera have the following activities: 55.6 mU/ml in Bos taurus L. (bull, "Morucha" race), 31.3 mU/ml in Sus scropha var. domestica L. (pig) and 3.7 mU/ml in Capra hircus L. (goat). 2. The pH optima of the enzymes are 4.5 for Bos taurus L. and Sus scropha L., and 5.0 for Capra hircus L. 3. Two enzyme forms, A and B, have been separated from Bos taurus L. and Capra hircus L. sera by DEAE-cellulose chromatography; and three forms, A, B and S, from Sus scropha L. serum. 4. The B forms are more heat-stable than the A and the S forms. The S form has intermediate heat-stability between the A and the B forms.     

Performance of crosses among flint maize populations under infestation by Sesamia nonagrioides (Lepidoptera: Noctuidae)

Flint maize, Zea mays L., varieties provide some interesting agronomic characteristics and kernels that possess a better ability than other kernels for developing high-quality flour. The pink stem borer, Sesamia nonagrioides Lefebvre, is an important constraint for the maize crop in Mediterranean regions. The objective of this work was to identify a "flint x flint" heterotic pattern that would perform well under artificial infestation by S. nonagrioides. A 10-population diallel was evaluated under infestation by S. nonagrioides in 2 yr. Variety effects were the only significant effects involved in stem and ear resistance to S. nonagrioides attack. Variety effects and average heterosis effects were the only significant effects for grain yield under artificial infestation conditions. Considering variety effects and cross-performance, the heterotic pattern Basto/Enano levantixo x Longfellow (BA/EL x LO) would be recommended for obtaining flint maize hybrids tolerant to S. nonagrioides attack because BA/EL had the most favorable variety effects for stem resistance, LO exhibited the most positive variety effects for grain yield, and the cross BA/EL x LO yielded significantly more than the remaining crosses.     

DNA polymorphism analysis of candidate genes for type 2 diabetes mellitus in a Mexican ethnic group

Type 2 diabetes mellitus is a complex metabolic disorder resulting from the action and interaction of many genetic and environmental factors. It has been reported that polymorphisms in genes involved in the metabolism of glucose are associated with the susceptibility to develop type 2 diabetes mellitus. Although the risk of developing type 2 diabetes mellitus increases with age, as well as with obesity and hypertension, its prevalence and incidence are different among geographical regions and ethnic groups. In Mexico, a higher prevalence and incidence has been described in the south of the country, and differences between urban and rural communities have been observed.We studied 73 individuals from Santiago Jamiltepec, a small indigenous community from Oaxaca State, Mexico. This population has shown a high prevalence of type 2 diabetes mellitus, and the aim of this study was to analyze the relationship between the Pst I (insulin gene), Nsi I (insulin receptor gene) and Gly972Arg (insulin receptor substrate 1 gene) polymorphisms and type 2 diabetes mellitus, obesity and hypertension in this population. Clinical evaluation consisted of BMI and blood pressure measurements, and biochemical assays consisted of determination of fasting plasma insulin and glucose levels. PCR and restriction enzyme digestion analysis were applied to genomic DNA to identify the three polymorphisms. From statistical analysis carried out here, individually, the Pst I, Nsi I and Gly972Arg polymorphisms were not associated with the type 2 diabetes, obese or hypertensive phenotypes in this population. Nevertheless, there was an association between the Nsi I and Pst I polymorphisms and increased serum insulin levels.     

The effect of the seed coat, embryonic axis and aeration conditions on starch degradation hi cotyledons of Lens culinaris

The effect of exogenously applied galactose on the cell wall polysaccharide synthesis and UDP-sugar levels in oat ( Avena sativa L. cv. Victory I) coleoptile segments was studied to clarify the mechanism of inhibition of IAA-induced cell elongation by galactose, and the following results were obtained: (1) The inhibition of IAA-induced cell elongation by galactose became apparent after a 2 h-lag, while the lag was shortened to 1 h when galactose was added to the segments after more than 1 h of IAA application. (2) Galactose inhibited the [¹⁴C]-glucose incorporation into cellulosic and non-cellulosic fractions of the cell wall and the increase in net polysaccharide content in the fractions during long-term incubation. (3) The dominant sugar nucleotide in oat coleoptiles was UDP-glucose (2.1 nmol segment⁻¹). Galactose application caused a remarkable decrease in the UDP-glucose level, accompanying a strong accumulation of galactose-1-phosphate and UDP-galactose. (4) Galactose-1-phosphate competitively inhibited the UTP: a- d -glucose-1-phosphate uridylyltransferase (EC 2.7.7.9) activity of the crude enzyme preparation from oat coleoptiles. From these results we conclude that galactose inhibits the IAA-induced cell elongation by inhibiting the formation of UDP-glucose, which is a key intermediate of cell wall polysaccharide synthesis.     

Molecular weight distribution of hemicellulosic polysaccharides of the cell wall of tall and dwarf rice cultivars, and the effect of GA3

Growth rate, osmotic potential of the cell, cell wall mechanical properties, sugar composition and molecular weight (MW) distribution of water-soluble hemicellulosic polysaccharides of the second leaf sheath of one tall ( Oryza sativa L. cv. Nihonbare) and two dwarf ( Oryza sativa L. cvs. Tan-ginbozu and Waito C) cultivars of rice were compared. The effect of gibberellic acid (GA₃) on the above-mentioned parameters was also studied using the tall (Nihonbare) and one of the dwarf (Waito C) cultivar. The minimum stress-relaxation time (T₀) was higher in the cell wall from the two dwarfs than in the tall cultivar. Furthermore, in the water-soluble hemicellulosic polysaccharides the mass-average MW of β -glucan was higher and that of arabinoxylan was lower in the tall cultivar than in the dwarf ones. Thus, dwarfism of cvs Tan-ginbnozu and Waito C might be correlated with the different MW distributions of β -glucan and arabinoxylan. GA₃ induces growth in the dwarf Waito C cultivar, decreases the T₀ value of the cell wall, and also decreases the average MW of water-soluble hemicelluloses. Changes in β (1–3)(1–4)glucan or arabinoxylan or in both are proposed as part of the cell wall loosening mechanism induced by gibberellin.     

Zerumbone induced apoptosis in liver cancer cells via modulation of Bax/Bcl-2 ratio

Background  

Zerumbone is a cytotoxic component isolated from Zingiber zerumbet Smith, a herbal plant which is also known as lempoyang. This new anticancer bioactive compound from Z. zerumbet was investigated for its activity and mechanism in human liver cancer cell lines.