Reaction: malonyl-CoA + 6 (2S)-methylmalonyl-CoA + 5 NADPH + 5 H+ = narbonolide + 7 CoA + 7 CO2 + 5 NADP+ + 2 H2O
For diagram of reaction click here.
Other name(s): pikromycin PKS
Systematic name: (2S)-methylmalonyl-CoA:malonyl-CoA malonyltransferase (narbonolide forming)
Comments: The product, narbonolide, contains a 14-membered ring and is an intermediate in the biosynthesis of narbonomycin and pikromycin in the bacterium Streptomyces venezuelae. The enzyme also produces 10-deoxymethynolide (see EC 2.3.1.239, 10-deoxymethynolide synthase). The enzyme has 29 active sites arranged in four polypeptides (pikAI - pikAIV) with a loading domain, six extension modules and a terminal thioesterase domain. Each extension module contains a ketosynthase (KS), keto reductase (KR), an acyltransferase (AT) and an acyl-carrier protein (ACP). Not all active sites are used in the biosynthesis.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number:
References:
1. Lu, H., Tsai, S.C., Khosla, C. and Cane, D.E. Expression, site-directed mutagenesis, and steady state kinetic analysis of the terminal thioesterase domain of the methymycin/picromycin polyketide synthase. Biochemistry 41 (2002) 12590-12597. [PMID: 12379101]
2. Kittendorf, J.D., Beck, B.J., Buchholz, T.J., Seufert, W. and Sherman, D.H. Interrogating the molecular basis for multiple macrolactone ring formation by the pikromycin polyketide synthase. Chem. Biol. 14 (2007) 944-954. [PMID: 17719493]
3. Yan, J., Gupta, S., Sherman, D.H. and Reynolds, K.A. Functional dissection of a multimodular polypeptide of the pikromycin polyketide synthase into monomodules by using a matched pair of heterologous docking domains. Chembiochem 10 (2009) 1537-1543. [PMID: 19437523]
4. Whicher, J.R., Dutta, S., Hansen, D.A., Hale, W.A., Chemler, J.A., Dosey, A.M., Narayan, A.R., Hakansson, K., Sherman, D.H., Smith, J.L. and Skiniotis, G. Structural rearrangements of a polyketide synthase module during its catalytic cycle. Nature 510 (2014) 560-564. [PMID: 24965656]