Alteration of the 2-Oxoacid Cosubstrate Selectivity in Deacetoxycephalosporin C Synthase: The Role of Arginine-258Lee, H.J., Lloyd, M.D., Harlos, K., Clifton, I.J., Baldwin, J.E., Schofield, C.J.
(2001) J Biol Chem 276: 18290
- PubMed: 11279000
- DOI: 10.1074/jbc.M100085200
- Primary Citation of Related Structures:
- PubMed Abstract:
- Studies on the Active Site of Deacetoxycephalosporin C Synthase
Lloyd, M.D., Lee, H.J., Harlos, K., Zhang, Z.H., Baldwin, J.E., Schofield, C.J., Charnock, J.M., Garner, C.D., Hara, T., Van Scheltinga, A.C.T., Valegard, K., Viklund, J.A.C., Hajdu, J., Andersson, I., Danielsson, A., Bhikhabhai, R.
(1999) J Mol Biol 287: 943
Deacetoxycephalosporin C synthase is an iron(II) 2-oxoglutaratedependent oxygenase that catalyzes the oxidative ring-expansion of penicillin N to deacetoxycephalosporin C. The wild-type enzyme is only able to efficiently utilize 2-oxoglutarate and 2-oxoadipate as a 2-oxoacid co-substrate ...
Deacetoxycephalosporin C synthase is an iron(II) 2-oxoglutaratedependent oxygenase that catalyzes the oxidative ring-expansion of penicillin N to deacetoxycephalosporin C. The wild-type enzyme is only able to efficiently utilize 2-oxoglutarate and 2-oxoadipate as a 2-oxoacid co-substrate. Mutation of arginine 258, the side chain of which forms an electrostatic interaction with the 5-carboxylate of the 2-oxoglutarate co-substrate, to a glutamine residue reduced activity to about 5% of the wild-type enzyme with 2-oxoglutarate. However, other aliphatic 2-oxoacids, which were not co-substrates for the wild-type enzyme, were utilized by the R258Q mutant. These 2-oxoacids "rescued" catalytic activity to the level observed for the wild-type enzyme as judged by penicillin N and G conversion. These co-substrates underwent oxidative decarboxylation as observed for 2-oxoglutarate in the normal reaction with the wild-type enzyme. Crystal structures of the iron(II)- 2-oxo-3-methylbutanoate (1.5 A), and iron(II)-2-oxo-4-methylpentanoate (1.6 A) enzyme complexes were obtained, which reveal the molecular basis for this "chemical co-substrate rescue" and help to rationalize the co-substrate selectivity of 2-oxoglutaratedependent oxygenases.
Oxford Centre for Molecular Sciences and the Dyson Perrins Laboratory, South Parks Road, Oxford OX1 3QY, United Kingdom.