A thermoactive uropygial esterase from chicken: Purification, characterisation and synthesis of flavour esters

Abstract

A lipolytic activity was located in the chicken uropygial glands, from which a carboxylesterase (CUE) was purified. Pure CUE has an apparent molecular mass of 50kDa. The purified esterase displayed its maximal activity (200U/mg) on short-chain triacylglycerols (tributyrin) at a temperature of 50°C. No significant lipolytic activity was found when medium chain (trioctanoin) or long chain (olive oil) triacylglycerols were used as substrates. The enzyme retained 75% of its maximal activity when incubated during 2h at 50°C. The NH2-terminal amino acid sequence showed similarities with the esterase purified recently from turkey pharyngeal tissue. Esterase activity remains stable after its incubation during 30min in presence of organic solvents such as hexane or butanol. CUE is a serine enzyme since it was inactivated by phenylmethanesulphonyl fluoride (PMSF), a serine-specific inhibitor. The purified enzyme, which tolerates the presence of some organic solvent and a high temperature, can be used in non-aqueous synthesis reactions. Hence, the uropygial esterase immobilised onto CaCO3 was tested to produce the isoamyl and the butyl acetate (flavour esters). Reactions were performed at 50°C in presence of hexane. High synthesis yields of 91 and 67.8% were obtained for isoamyl and butyl acetate, respectively.