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Biomedical subjects

O R Zaborsky

Publications and source records attributed to O R Zaborsky.

11 recordsLinked to original sources
PubMed1975

Structural effects on the reactivity of substrates and inhibitors in the epoxidation system of Pseudomonas oleovorans.

The epoxidation reaction catalyzed by an enzyme system of Pseudomonas oleovorans exhibits a substrate specificity different from that expected on the basis of chemical reactivity in non-enzymatic epoxidation reactions. Cyclic and internal olefins, aromatic compounds and styrene are not epoxidated. The reactivity of straight chain diolefins is maximal for octadiene and falls off rapidly as the carbon chain is shortened, but decreases only slightly as the chain is lengthened. In contrast, methyl group hydroxylation is less sensitive to decreasing chain length. As a consequence, propylene and 1-butene are hydroxylated but not epoxidated by this enzyme system. With the substrate 1-decene, which is capable of undergoing both epoxidation and hydroxylation, the former reaction predominates. Methyl imidoesters were found to be inhibitors of enzymatic epoxidation, and the potency of a homologous series of imidoester inhibitors was examined. The results parallel the substrate specificity patterns observed, and support the conclusion that the mode of substrate binding severely moderates the inherent chemical reactivity of the activated oxygen in this system. The effect of the bifunctional imidoester, dimethyladipimidate, was also examined and the results compared with those obtained in other investigations.

Alcohols↗
PubMed1975

Circular dichroism of protocatechuate 3,4-dioxygenase from Pseudomonas aeruginosa.

The circular dichroism spectrum of protocatechuate 3,4-dioxygenase from Pseudomonas aeruginosa has been examined in the absence of the substrates, protocatechuic acid and O-2 and in the presence of the competitive inhibitors, protocatechualdehyde and p-hydroxybenzoic acid. The native enzyme has a low alpha-helical content (less than 1%) and exhibits several positive ellipticity bands between 250 and 300 nm (255,269,275 and 292 nm) and two, low intensity, negative bands at 330 and 480 nm. In the presence of protocatechuic acid and the absence of O-2, spectral changes are evident in the side chain and visible regions. There is a shift in the aromatic-region maximum from 275 to 267 and in the visible region from 330 to 348 and from 480 to 555 nm. No spectral changes are observed upon the removal or addition of only O-2. Different spectral changes in both the side chain and visible regions are observed in the enzyme with the two competitive inhibitors under either aerobic or anaerobic conditions. The spectral changes observed in the side chain region suggest the possible participation of aromatic residues in the binding process, but it is not yet established as to whether these residues play an active or passive role in binding and/or catalysis.

Aldehydes↗