The production of enantiomerically pure amino acids is of industrial importance as they are used in the synthesis of a number of pharmaceuticals, insecticides and herbicides and biologically active peptides and hormones. A number of microorganisms have been identified which possess hydantoin hydrolysing enzymes that stereoselectively convert racemic hydantoins into anantiomerically pure amino acids. Consequently these microorganisms and their enzymes are sought after as biocatalysts for the production of amino acids. The isolation of novel hydantoin hydrolising enzymes with unique or improved biocatalytic characteristics is of importance for the development of potential biocatalysts to be used in the production of enantiomerically pure amino acids. The genes encoding an N-carbamoyl-amino acid amidohydrolase, an enzyme involved in the hydrolysis of hydantoin, was isolated by screening a genomic DNA library of Agrobacterium tumefacience RU-AE01. Nucleotide sequence analysis of the region upstream of this gene revealed a fragment of a gene encoding the hydantoinase enzyme. I this study, a DNA probe consisting of the gene encoding the N-carbamoyl amino acid amidohydrolase, on a large enough fragment of the genomic DNA library which would allow for the simultaneous isolation the hydantoinase gene located upstream. Recombinant expression of the genes encoding hydantoin hydrolysing enzymes has been used to facilitate the production and purification of these enzymes for their use as biocatalysts. Two genes (ncaR1 and ncaR2) encoding different N-carbamoyl-amino acid amidohydrolases with distinct nucleotide and deduced amino acid sequences were isolated from the genome of A, tumefaciens RU-OR. In this study, the heterologous expression of ncaR1 and ncaR2 was explored. Investigation into the optimisation of the heterologous expression of ncaR1 showed that reducing the growth temperature of the recombinant E. coli producing NcaR1 resulted in a two-fold increase in N-carbamoyl-amino acid amidohydrolase activity and solubility. Furthermore, NcaR1 was produced with a C-terminal 6xHis tag, but NcaR1-6xHis did not possess N-carbamoyl amino acid amidohydrolase activity. Furthermore, purification of NcaR-6xHis under native conditions using affinity chromatography performed, and used for the production of antibodies.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:rhodes/vital:4140 |
| Date | January 2003 |
| Creators | Clark, Sally-Ann |
| Publisher | Rhodes University, Faculty of Science, Biochemistry and Microbiology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis, Masters, MSc |
| Format | 171 leaves, pdf |
| Rights | Clark, Sally-Ann |
Page generated in 0.0021 seconds