Publications

• Structural and functional analysis of tetracenomycin F2 cyclase from Streptomyces glaucescens. A type II polyketide cyclase.

  Thompson T.B., Katayama K., Watanabe K., Hutchinson C.R., Rayment I.

  Tetracenomycin F2 cyclase (tcmI gene product), catalyzes an aromatic rearrangement in the biosynthetic pathway for tetracenomycin C in Streptomyces glaucescens. The x-ray structure of this small enzyme has been determined to 1.9-A resolution together with an analysis of site-directed mutants of po ... >> More

  Tetracenomycin F2 cyclase (tcmI gene product), catalyzes an aromatic rearrangement in the biosynthetic pathway for tetracenomycin C in Streptomyces glaucescens. The x-ray structure of this small enzyme has been determined to 1.9-A resolution together with an analysis of site-directed mutants of potential catalytic residues. The protein exhibits a dimeric betaalphabeta ferredoxin-like fold that utilizes strand swapping between subunits in its assembly. The fold is dominated by four strands of antiparallel sheet and a layer of alpha-helices, which creates a cavity that is proposed to be the active site. This type of secondary structural arrangement has been previously observed in polyketide monooxygenases and suggests an evolutionary relationship between enzymes that catalyze adjacent steps in these biosynthetic pathways. Mutational analysis of all of the obvious catalytic bases within the active site suggests that the enzyme functions to steer the chemical outcome of the cyclization rather than providing a specific catalytic group. Together, the structure and functional analysis provide insight into the structural framework necessary to perform the complex rearrangements catalyzed by this class of polyketide cyclases. << Less

  J. Biol. Chem. 279:37956-37963(2004) [PubMed] [EuropePMC]

• Tetracenomycin F2 cyclase: intramolecular aldol condensation in the biosynthesis of tetracenomycin C in Streptomyces glaucescens.

  Shen B., Hutchinson C.R.

  Tetracenomycin (Tcm) F2 cyclase, which catalyzes the cyclization of the anthrone Tcm F2 to the naphthacenone Tcm F1 in the biosynthesis of the anthracycline antibiotic Tcm C in Streptomyces glaucescens, has been purified to homogeneity and characterized. The N-terminal sequence of the enzyme estab ... >> More

  Tetracenomycin (Tcm) F2 cyclase, which catalyzes the cyclization of the anthrone Tcm F2 to the naphthacenone Tcm F1 in the biosynthesis of the anthracycline antibiotic Tcm C in Streptomyces glaucescens, has been purified to homogeneity and characterized. The N-terminal sequence of the enzyme establishes that it is encoded by the tcmI gene, whose deduced product has a molecular weight of 12,728. SDS-PAGE analysis gave a single band with a molecular weight of 12,500, whereas gel-filtration chromatography yielded a molecular weight of 37,500, indicating that the Tcm F2 cyclase is a homotrimer in solution. Under pH > or = 8.0, the enzyme catalyzes the cyclization of Tcm F2 to Tcm F1 and has a Km of 121 +/- 18.2 microM and Vmax of 704 +/-62.3 nmol.min-1.mg-1. In contrast, under pH < or = 6.5, it catalyzes the cyclization of Tcm F2 to 9-decarboxy Tcm F1, a known shunt metabolite of the Tcm C biosynthetic pathway. Tcm F2 cyclase represents the first discrete enzyme for carbon-carbon bond formation via an intramolecular aldol condensation-dehydration mechanism, a key biochemical operation proposed in the early steps of the biosynthesis of all aromatic polyketides. << Less

  Biochemistry 32:11149-11154(1993) [PubMed] [EuropePMC]