title: Kinetic and thermodynamic investigation of enzymatic L-ascorbyl acetate synthesis.
abstract: Kinetics and thermodynamics of lipase-catalyzed esterification of l-ascorbic acid in acetone were investigated by using vinyl acetate as acyl donor. The results showed that l-ascorbic acid could generate inhibition effect on lipase activity. A suitable model, Ping-Pong Bi-Bi mechanism having substrate inhibition, was thus introduced to describe the enzymatic kinetics. Furthermore, the kinetic and thermodynamic parameters were calculated from a series of experimental data according to the kinetic model. The inhibition constant of L-ascorbic acid was also obtained, which seemed to imply that enhancing reaction temperature could depress the substrate inhibition. Besides, the activation energy values of the first-step and the second-step reaction were estimated to be 37.31 and 4.94 kJ/mol, respectively, demonstrating that the first-step reaction was the rate-limiting reaction and could be easily improved by enhancing temperature.
authors.affiliation: College of Pharmacy, Hebei University, Baoding 071002, China; Key Laboratory of Pharmaceutical Quality Control of Hebei Province, College of Pharmacy, Hebei University, Baoding 071002, China. Electronic address: zhangdonghao1@gmail.com.
authors.forename: Dong-Hao
authors.initials: DH
authors.lastname: Zhang
authors.forename: Chao
authors.initials: C
authors.lastname: Li
authors.forename: Gao-Ying
authors.initials: GY
authors.lastname: Zhi
mesh_terms: D001205:Ascorbic Acid / Q000096:biosynthesis* / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D004800:Enzymes, Immobilized; D004951:Esterification; D032641:Eurotiales / Q000201:enzymology*; D007700:Kinetics; D008049:Lipase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D008956:Models, Chemical; D013379:Substrate Specificity; D013816:Thermodynamics; D014753:Vinyl Compounds / Q000737:chemistry
chemical_list: D004800:Enzymes, Immobilized; D014753:Vinyl Compounds; D008049:Lipase; C011566:vinyl acetate; D001205:Ascorbic Acid
keywords: Activation energy; Kinetic model; Ping-Pong Bi-Bi mechanism; Substrate inhibition; l-Ascorbic acid