Development of a high throughput screening tool for biotransformations utilising a thermophilic l-aminoacylase enzyme

Micro-reactors containing a monolith-immobilised thermophilic l-aminoacylase, from Thermococcus litoralis, have been developed for use in biotransformation reactions and a study has been carried out to investigate the stereospecificity and stability of the immobilised enzyme. The potential to use the developed micro-reactors as a tool for rapid screening of enzyme specificity was demonstrated, confirming that the l-aminoacylase showed a similar substrate specificity to that previously reported of the free enzyme. From this baseline, the technique was employed as a tool to evaluate potential unreported substrates with N-benzoyl- (l-threonine, l-leucine and l-arginine) and N-acetyl- (d,l-serine, d,l-leucine, l-tyrosine and l-lysine) protecting groups. The order of preferred substrates was found to be Phe > Thr > Leu > Arg for N-benzoyl substrates and Phe ≫ Ser > Leu > Met > Tyr > Trp for N-acetyl substrates.It was found that by using the micro-reactor a significantly smaller quantity of enzyme and substrates was required. It was shown that the micro-reactors were still operational in the presence of selected organic solvents, such as ethanol, methanol, acetone, dimethylformamide (DMF) and dimethylsulfoxide (DMSO). The results indicated that a combination of a small amount of an appropriate solvent (5% DMSO) and a higher reaction temperature could be employed in biotransformations where substrate solubility was an issue.