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Tyr 64, hydrogen-bonded to coenzyme phosphate in Treponema denticola cystalysin is changed to alanine by site-directed mutagenesis, spectroscopic and kinetic properties of the Tyr 64 are investigated to explore the differences in coenzyme structure and kinetic mechanism to those of wild type enzyme. The result finds new insight into the catalytic mechanism of cystalysin and highlights the functional role of Tyr 64.

Research has been conducted on Treponema denticola cystalysin. The functional properties of this cystalysin have been investigated via the pH- and ligand-induced spectral transition analysis and the results suggest that cystalysin is more catalytically competent in alkaline solution.

The inactivation of dopa decarboxylase (DDC) by the inhibitors serotonin and dopamine was investigated. Recombinant DDC was purified to homogeneity with slight modification for use in the study. Results showed that the kinetics of DDC inactivation by serotonin and dopamine is consistent with the conversion of both inhibitors to 5-hydroxyindolacetaldehyde and 3,4-dihydroxyphenylacetaldehyde, respectively. In addition, the mechanism of DDC inactivation probably involves generation of an active site directed affinity label, 3,4-dihydroxyphenylacetone.

The unusual oxygen-consuming oxidative deamination reaction catalyzed by the pyridoxal 5'-phosphate (PLP) enzyme DOPA decarboxylase (DDC) is examined. The catalytic properties of the T246A DDC mutant has shown that the Thr246-His192 dyad could act as a general base in promoting the first step of the oxidative deamination of aromatic amines.

The protein misfolding cyclic amplification (PMCA) and scrapie cell assay (SCA) techniques are used to study the role of N-linked glycosylation on prion formation in vitro. The results have shown that the interactions between different Pr[P.sup.C] (host-encoded glycoprotein) glycoforms control the efficiency of prion formation in a species-specific manner.