Marked dependence of enzyme prochiral selectivity on the solvent

Abstract

390J. Am. Chem. SOC. with 0.37 unit of transcarboxylase in 20 p L containing KP, (250 mM, pH 7.0) and DTT (IO mM) at 25 OC. After 1 min the incubation was centrifuged through two spun-dry DE52 ( I mL wet) beds in sequence in the cold within 10 min. The 14C radioactivity and enzyme activity of the second filtrate were compared. This ratio was determined as a function of the MMCoA concentration used to label the enzyme: 0.05,0.1, and 0.25 mM. The limit, determined graphically, was 1280 cpm/unit of activity; i.e. 0.275 nmol of biotin could be carboxylated by MMCoA per unit of activity. This value is -40% greater than the highest value reported by Wood et a1.I0 on the basis of the counts of labeled biotin 1993,115, 390-396 incorporated and the highest enzyme activity that was obtained in the same assay. The difference can be attributed to loss during storage of the assay rate, which depends on the coordinated function of the two half-reactions, without loss of capacity for the MMCoA/propionyl CoA half-reaction.* Acknowledgment.Abstract: Prochiral selectivity of various hydrolytic enzymes (lipases and proteases) in organic solvents was investigated in transformations involving a 2-substituted 1,3-propanedioI or its diester. In two instances, a significant dependence of enzyme prochiral selectivity on the solvent was found: transesterification of diol 1 with vinyl butyrate catalyzed by Aspergillus oryzae protease in anhydrous solvents and hydrolysis of diester 3 catalyzed by Pseudomonas sp. lipase in hydrated organic solvents (monoester 2 was a product in both reactions). The latter process, where the p r o 4 selectivity of the enzyme varied from around 3 in some solvents to greater than 30 in others, was examined in more detail. A mechanistic model was proposed that predicted an inverse correlation between lipase's prochiral selectivity and solvent hydrophobicity, as well as particular effects of substrate structure variation and an additive on the prochiral selectivity; all these predictions were confirmed experimentally. Subtilisin Carlsberg lacked appreciable prochiral selectivity in either transesterification or hydrolysis reactions regardless of the solvent; this was rationalized by means of interactive computer modeling based on the X-ray crystal structure of this serine protease.

Stability and activity of lipase in subcritical 1,1,1,2-tetrafluoroethane (R134a)

“…Incubated with subcritical R134a at 30-60°C, an enzyme activity increase for several-fold (maximum of 300% of the initial activity at 30°C) was observed. In contrast to SC-CO 2 treatment, which presented activity loss (5%) for Novozym 435 at 55°C [26], no loss of enzyme activity was observed when Novozym 435 exposure to subcritical R134a, even at 60°C. The extent to which enzymes show thermostability depends on the hydrophobicity of the media and the type of enzyme.…”

“…Pressurized R134a is more hydrophobic than pressurized CO 2, although it seems hydrophilic being judged from other parameters such as permittivity and polarity parameter [13]. As indicated by many researches in which enzyme activity and stability in organic solvents increased with hydrophobic property (logP) of the solvents [16,25,26], pressurized R134a, with regard to its hydrophobic parameter, may be a promising medium for enzyme-catalyzed reactions.…”

Lipase-catalyzed irreversible transesterification of 1-(2-furyl)ethanol using isopropenyl acetate

“…24,25 It has been reported that solvents with log P values more than two exhibit high enantioselectivity, whereas solvents with log P less than two show detrimental effects on the enzymes. 26 P is employed as an index for the solvent hydrophobicity in biocatalytic reactions 27 and is defined as the ratio of the concentration of a substance in two immiscible phases at equilibrium (octanol and water). Several solvents (isooctane: log P = 4.5, TBME: log P = 1.35, n-hexane: log P = 3.5, n-heptane: log P = 4, toluene: log P = 2.5) were investigated for the transesterification of 1 at 40°C in the presence of molecular sieves 4 Å ( Table 2).…”

Organo-gel: um novo sistema para a imobilização de lipases e sua aplicação em síntese orgânica

“…Perda em eficiência catalítica e enantiosseletividade foram observadas quando a lipase de Candida cilindracea foi empregada em meio orgânico hidrofílico tal como dioxano ou tetrahidrofurano, comparativamente com solventes hidrofóbicos como por exemplo o tolueno 132 . A seletividade pró-quiral de uma enzima pode também ser grandemente afetada pelo solvente 133 . Para investigar o efeito do solvente no sistema de organo-gel (MBG), diferentes solventes foram utilizados na reação de esterificação do ácido oleico e 1-pentanol.…”