BIOCHEMICAL CHARACTERIZATION OF AN EU- CARIOTIC POLYKETIDE SYNTHASE

ANA ARABOLAZA; SABATINI MARTIN; SILVIA ALTABE; GRAMAJO HUGO; COMBA SANTIAGO

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

Methyl-branched fatty acids (FA) are compounds which have nu-merous industrial applications. They show improved physicochem-ical properties in comparison to linear carbon chain FA, the mostcommon FA found in natural sources. However, this kind of mole-cules is extremely rare in nature. Thus, with the aim to develop newcompounds with optimized properties for industrial uses, in this workwe explored a new strategy to generate structural diversity in FA.Based on the mycoserosic acid synthase (MAS), a polyketidesynthase (PKS) from Mycobacterium tuberculosis that synthesizeslong chain methyl-branched fatty acids, we searched for a new PKScapable of using methylmalonyl-CoA (MMC) as extender unit. UsingMAS as query for a BLASTp search, we identified a new family ofun-characterized and highly conserved PKS in birds. The uropygialgland, in birds, is involved in the secretion of methyl-branched fattyacids, alcohols and esters that are used for cleaning and imperme-abilization of the plumage. We hypothesized that these compoundswould be produced by this new family of PKS. In particular, we start-ed the characterization of a PKS enzyme, that we named ApMAS,from the duck Anas platyrhynchos; in this specie the uropygial se-cretion has a high proportion of methyl-branched- C6 FA.PKS are enzymatic complexes that condense simple short chainacyl-CoA into larger molecules with diverse biological activities. Inan initial biochemical analysis of ApMAS, we determined the abilityof this enzyme to covalently bind to the substrates by using radio-labeled precursors, acetyl-CoA/propionyl-CoA as starter units andmalonyl-CoA/MMC as extender units. Using this strategy we couldalso evidence the substrate transfer from an acyl-CoA to the ApMASacyl carrier protein domain (ACP). We then measured the kineticsof this transfer reaction catalized by the ApMAS acyltransferase do-main. Finally, we could demonstrate the in vitro condensing ability ofthe ApMAS ketosynthase domain.