L-Asparaginase Conjugates from the Hyperthermophilic Archaea Thermococcus sibiricus with Improved Biocatalytic Properties.

This study investigated the effect of polycationic and uncharged polymers (and oligomers) on the catalytic parameters and thermostability of L-asparaginase from Thermococcus sibiricus (TsA). This enzyme has potential applications in the food industry to decrease the formation of carcinogenic acrylamide during the processing of carbohydrate-containing products. Conjugation with the polyamines polyethylenimine and spermine (PEI and Spm) or polyethylene glycol (PEG) did not significantly affect the secondary structure of the enzyme. PEG contributes to the stabilization of the dimeric form of TsA, as shown by HPLC. Furthermore, neither polyamines nor PEG significantly affected the binding of the L-Asn substrate to TsA. The conjugates showed greater maximum activity at pH 7.5 and 85 °C, 10-50% more than for native TsA. The pH optima for both TsA-PEI and TsA-Spm conjugates were shifted to lower pH ranges from pH 10 (for the native enzyme) to pH 8.0. Additionally, the TsA-Spm conjugate exhibited the highest activity at pH 6.5-9.0 among all the samples. Furthermore, the temperature optimum for activity at pH 7.5 shifted from 90-95 °C to 80-85 °C for the conjugates. The thermal inactivation mechanism of TsA-PEG appeared to change, and no aggregation was observed in contrast to that of the native enzyme. This was visually confirmed and supported by the analysis of the CD spectra, which remained almost unchanged after heating the conjugate solution. These results suggest that TsA-PEG may be a more stable form of TsA, making it a potentially more suitable option for industrial use.

Complete mitochondrial genome of the cephalosporin-producing fungus Acremonium chrysogenum.

Complete nucleotide sequence of the 27,266 bp mitochondrial genome of the сephalosporin C producing fungus Acremonium chrysogenum have been determined using whole genome shotgun sequencing approach. The circular mapping molecule encodes a usual set of mitochondrial proteins and RNA genes, including large and small ribosomal RNAs, 19 proteins and 26 tRNA genes and contains 2 introns. All structural genes are located on one strand and are apparently transcribed in one direction. Comparative analysis of this and previously sequenced Pezizomycotina mtDNAs revealed more extensive similarity between A. chrysogenum genome and those of Fusarium clade and specific synthenic patterns characteristic of Hypocrealean mitogenomes. Phylogenetic analysis based on catenated mitochondrial protein sequences confirmed current taxonomic position of A. chrysogenum within Hyprocreales and related taxa.

Draft Genome Sequence of Escherichia coli Strain VKPM B-10182, Producing the Enzyme for Synthesis of Cephalosporin Acids.

Escherichia coli strain VKPM B-10182, obtained by chemical mutagenesis from E. coli strain ATCC 9637, produces cephalosporin acid synthetase employed in the synthesis of ß-lactam antibiotics, such as cefazolin. The draft genome sequence of strain VKPM B-10182 revealed 32 indels and 1,780 point mutations that might account for the improvement in antibiotic synthesis that we observed.