%0 Journal Article
%T The reductase domain in a Type I fatty acid synthase from the apicomplexan Cryptosporidium parvum: Restricted substrate preference towards very long chain fatty acyl thioesters
%A Guan Zhu
%A Xiangyu Shi
%A Xiaomin Cai
%J BMC Biochemistry
%D 2010
%I BioMed Central
%R 10.1186/1471-2091-11-46
%X In the present study, the identity of CpFAS1-R as a reductase is confirmed by in silico analysis on sequence similarity and characteristic motifs. Phylogenetic analysis based on the R-domains supports a previous notion on the bacterial origin of apicomplexan Type I FAS/PKS genes. We also developed a novel assay using fatty acyl-CoAs as substrates, and determined that CpFAS1-R could only utilize very long chain fatty acyl-CoAs as substrates (i.e., with activity on C26 > C24 > C22 > C20, but no activity on C18 and C16). It was capable of using both NADPH and NADH as electron donors, but prefers NADPH to NADH. The activity of CpFAS1-R displayed allosteric kinetics towards C26 hexacosanoyl CoA as a substrate (h = 2.0; Vmax = 32.8 nmol min-1 mg-1 protein; and K50 = 0.91 mM).We have confirmed the activity of CpFAS1-R by directly assaying its substrate preference and kinetic parameters, which is for the first time for a Type I FAS, PKS or non-ribosomal peptide synthase (NRPS) reductase domain. The restricted substrate preference towards very long chain fatty acyl thioesters may be an important feature for this megasynthase to avoid the release of product(s) with undesired lengths.Cryptosporidium is a group of important parasites that infect a wide range of hosts from reptiles and birds to humans and other mammals [1-3]. Among them, C. parvum is zoonotic and infects both humans and animals. Cryptosporidium infection in immunocompetent individuals may cause self-limiting diarrhea, but its infection in immunocompromized patients can be chronic and life-threatening [4,5]. Therefore, it is an important opportunistic pathogens in AIDS patients. Additionally, there are no effective treatments against cryptosporidial infection in AIDS patients.The Cryptosporidium genus belongs to the Phylum Apicomplexa that also contains many important human and animal parasites such as Plasmodium, Theileria, Toxoplasma, Eimeria and Cyclospora [6]. However, Cryptosporidium is known to be evolution
%U http://www.biomedcentral.com/1471-2091/11/46