Blakeslea trispora genes for carotene biosynthesis

We cloned the carB and carRA genes involved in beta-carotene biosynthesis from overproducing and wild-type strains of Blakeslea trispora. The carB gene has a length of 1,955 bp, including two introns of 141 and 68 bp, and encodes a protein of 66.4 kDa with phytoene dehydrogenase activity. The carRA gene contains 1,894 bp, with a single intron of 70 bp, and encodes a protein of 69.6 kDa with separate domains for lycopene cyclase and phytoene synthase. The estimated transcript sizes for carB and carRA were 1.8 and 1.9 kb, respectively. CarB from the beta-carotene-overproducing strain B. trispora F-744 had an S528R mutation and a TAG instead of a TAA stop codon. The overproducing strain also had a P143S mutation in CarRA. Both B. trispora genes could complement mutations in orthologous genes in Mucor circinelloides and could be used to construct transformed strains of M. circinelloides that produced higher levels of beta-carotene than did the nontransformed parent. The results show that these genes are conserved across the zygomycetes and that the B. trispora carB and carRA genes are functional and potentially useable to increase carotenoid production.

Biotechnological lycopene production by mated fermentation of Blakeslea trispora

A semi-industrial process (800-l fermentor) for lycopene production by mated fermentation of Blakeslea trispora plus (+) and minus (-) strains has been developed. The culture medium was designed at the flask scale, using a program based on a genetic algorithm; and a fermentation process by means of this medium was developed. Fermentation involves separate vegetative phases for (+) and (-) strains and inoculation of the production medium with a mix of both together. Feeding with imidazole or pyridine, molecules known to inhibit lycopene cyclase enzymatic activity, enhanced lycopene accumulation. Different raw materials and physical parameters, including dissolved oxygen, stirring speed, air flow rate, temperature, and pH, were checked in the fermentor to get maximum lycopene production. Typical data for the fermentation process are presented and discussed. This technology can be easily scaled-up to an industrial application for the production of this carotenoid nowadays widely in demand.

Direct enzymatic synthesis of natural penicillins using phenylacetyl-CoA: 6-APA phenylacetyl transferase of Penicillium chrysogenum: minimal and maximal side chain length requirements

In vitro synthesis of different natural penicillins (hexanoyl, heptanoyl and octanoyl-penicillin) have been carried out by direct acylation of 6-aminopenicillanic acid (6-APA) with several fatty acid-CoA derivatives (hexanoyl-CoA, heptanoyl-CoA and octanoyl-CoA). The reactions were catalyzed by the enzyme Acyl-CoA: 6-aminopenicillanic acid acyltransferase from Penicillium chrysogenum AS-P-78. This enzyme only accepts as substrate, aliphatic side chain precursors whose carbon length is between 6 and 8 atoms. Although the enzymatic synthesis of octanoylpenicillin has been previously reported the in vitro synthesis of hexanoyl and heptanoyl penicillins is described here for the first time.

Glucose represses formation of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine and isopenicillin N synthase but not penicillin acyltransferase in Penicillium chrysogenum

The content of alpha-aminoadipyl-cysteinyl-valine, the first intermediate of the penicillin biosynthetic pathway, decreased when Penicillium chrysogenum was grown in a high concentration of glucose. Glucose repressed the incorporation of [14C]valine into alpha-aminoadipyl-cysteinyl-[14C]valine in vivo. The pool of alpha-aminoadipic acid increased sevenfold in control (lactose-grown) penicillin-producing cultures, coinciding with the phase of rapid penicillin biosynthesis, but this increase was very small in glucose-grown cultures. Glucose stimulated homocitrate synthase and saccharopine dehydrogenase activities in vivo and increased the incorporation of lysine into proteins. These results suggest that glucose stimulates the flux through the lysine biosynthetic pathway, thus preventing alpha-aminoadipic acid accumulation. The repression of alpha-aminoadipyl-cysteinyl-valine synthesis by glucose was not reversed by the addition of alpha-aminoadipic acid, cysteine, or valine. Glucose also repressed isopenicillin N synthase, which converts alpha-aminoadipyl-cysteinyl-valine into isopenicillin N, but did not affect penicillin acyltransferase, the last enzyme of the penicillin biosynthetic pathway.

Direct evaluation of phenylacetyl-CoA: 6-aminopenicillanic acid acyltransferase of Penicillium chrysogenum by bioassay

The enzyme phenylacetyl-CoA: 6-Aminopenicillanic acid acyltransferase of Penicillium chrysogenum was evaluated by direct bioassay against Micrococcus luteus ATCC 9341. The enzyme required dithiothreitol, was inactivated by 0.2 mM Hg2+ (100%), Zn2+ (80%), Cu2+ (60%), 1 mM N-ethylmaleimide (80%), and showed maximal catalytic activity at pH 8.4 and 20 degrees C. The V50 values for phenylacetyl-CoA and 6-aminopenicillanic acid were 0.55 mM and 1 microM, respectively. When octanoyl-CoA was employed as substrate similar results were obtained. In both cases the product generated showed strong antibacterial activity which was quickly lost when incubation was carried out with beta-lactamase. Reactions performed in the presence of Escherichia coli penicillin acylase did not generated active products when phenylacetyl-CoA was the substrate; they did with octanoyl-CoA. Time-course experiments revealed that the highest enzyme levels are found in 36 hours mycelium and remained almost constant from 48 to 96 hours; thereafter the level of the enzyme slowly decreased.

Cyclization of phenylacetyl-L-cysteinyl-D-valine to benzylpenicillin using cell-free extracts of Streptomyces clavuligerus

Benzylpenicillin, a typical antibiotic produced by some species of fungi, was obtained by direct cyclization of the heteropeptide phenylacetyl-L-cysteinyl-D-valine using cell-free extracts of Streptomyces clavuligerus. This is the first description of evidence of the synthesis of benzylpenicillin from a non natural molecule using a bacterial enzyme.

Isopenicillin N synthetase of Penicillium chrysogenum, an enzyme that converts delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine to isopenicillin N

The tripeptide delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine, an intermediate in the penicillin biosynthetic pathway, is converted to isopenicillin N by isopenicillin N synthetase (cyclase) of Penicillium chrysogenum. The cyclization required dithiothreitol and was stimulated by ferrous ions and ascorbate. Co2+ and Mn2+ completely inhibited enzyme activity. Optimal temperature and pH were 25 degrees C and 7.8, respectively. The reaction required O2 and was stimulated by increasing the dissolved oxygen concentration of the reaction mixture. Purification of the enzyme to a single major band in polyacrylamide gel electrophoresis was achieved by protamine sulfate precipitation, ammonium sulfate fractionation (50 to 80% of saturation), DEAE-Sephacel chromatography, and gel filtration on Sephacryl S-200. The estimated molecular weight was 39,000 +/- 1,000. The apparent Km of isopenicillin N synthetase for delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine was 0.13 mM. The enzyme activity was strongly inhibited by glutathione, which acts as a competitive inhibitor. A good correlation was observed between the isopenicillin N synthetase activity in extracts of four different strains of P. chrysogenum (with widely different penicillin-producing capability) and the amount of penicillin production by these strains.

Carbon catabolite repression of penicillin biosynthesis by Penicillium chrysogenum

The addition of glucose to batch cultures of Penicillium chrysogenum AS-P-78 reduced the biosynthesis of penicillin. This regulatory effect was also observed in penicillin biosynthesis by nitrogen-limited resting cells when cultures were previously grown in high concentrations of glucose. The effect of glucose was concentration-dependent in the range of 28-140 mM. Incorporation of L-[U-14C]valine into penicillin in nitrogen-limited resting cultures was reduced by 70% when cells were grown on 140 mM glucose, as compared with that grown on lactose. It was not affected when the sugar was added to the resting cell system, in which penicillin biosynthesis took place without growth. Fructose, galactose and sucrose exerted the regulatory effect to the same extent as glucose (64 to 70%). Lactose did not exert suppression of penicillin biosynthesis. Penicillin-synthesizing activity in control cultures with lactose reached a peak at 24 hours of incubation and decreased slowly thereafter, as studied with resting cell cultures in which further protein synthesis was blocked with cycloheximide. Glucose repressed the formation of penicillin-synthesizing enzymes, but had no effect on the activity of these enzymes. These results suggest that glucose represses but does not inhibit penicillin biosynthesis.