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:  1HJG
- 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- ...
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.