Esterases receive special attention because their wide distribution in biological systems and environments and their importance for physiology and chemical synthesis. The prediction of esterases substrate promiscuity level from sequence data and the molecular reasons why certain such enzymes are more promiscuous than others, remain to be elucidated. This limits the surveillance of the sequence space for esterases potentially leading to new versatile biocatalysts and new insights into their role in cellular function. Here we performed an extensive analysis of the substrate spectra of 145 phylogenetically and environmentally diverse microbial esterases, when tested with 96 diverse esters. We determined the primary factors shaping their substrate range by analyzing substrate range patterns in combination with structural analysis and protein-ligand simulations. We found a structural parameter that helps ranking (classifying) promiscuity level of esterases from sequence data at 94% accuracy. This parameter, the active site effective volume, exemplifies the topology of the catalytic environment by measuring the active site cavity volume corrected by the relative solvent accessible surface area (SASA) of the catalytic triad. Sequences encoding esterases with active site effective volumes (cavity volume/SASA) above a threshold show greater substrate spectra, which can be further extended in combination with phylogenetic data. This measure provides also a valuable tool for interrogating substrates capable of being converted. This measure, found to be transferred to phosphatases of the haloalkanoic acid dehalogenase superfamily and possibly other enzymatic systems, represents a powerful tool for low-cost bioprospecting for esterases with broad substrate ranges, in large scale sequence datasets.
A toxicologic and dermatologic review of methyl cinnamate when used as a fragrance ingredient is presented.
Title: Isolation and identification of mercapturic acid metabolites of phenyl substituted acrylate esters from urine of female rats Delbressin LP, van Balen HC, Seutter-Berlage F Ref: Archives of Toxicology, 49:321, 1982 : PubMed
The urinary mercapturic acid excretion by female rats of methyl atropate (alpha-phenyl methyl acrylate) and methyl cinnamate (beta-phenyl methyl acrylate) has been studied. On the basis of the structures of these mercapturic acids the conclusion can be drawn that these compounds arise from a conjugation of glutathione with the acrylic esters in a Michael fashion. Previous administration of (tri-orthotolyl) phosphate (TOTP), a carboxy esterase inhibitor, enhances the capacity of the acrylate esters to alkylate glutathione in vivo. The amount increased from 1.5 to 22.8% of dose (1.0 mmol/kg) for methyl cinnamate and from 10.4 to 14.8% of dose (0.2 mmol/kg) for methyl atropate. Upon inhibition of the esterase activity the major actual mercapturic acid is a conjugate of the acrylate in which the ester function is retained. In the absence of an esterase inhibition the excreted mercapturic acid is a formal conjugate of the free acrylic acid (Fig. 1). No mercapturic acids could be detected which might arise from glutathione conjugation of a, beta-epoxyesters. Such epoxides are potential primary metabolites of unsaturated esters. They were not detected by in vitro experiments. Therefore, the intermediacy of glycidic esters in the biotransformation of these acrylic esters may be considered as highly unlikely.
