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Peroxidases (POD) of crude extracts from barley and wheat germ were separated, partially purified using salt fractionation, ion-exchange and hydrophobic interaction chromatographies and their properties examined. Barley and wheat germ POD contained basic, neutral and anionic isoforms as confirmed by isoelectric focusing. Toyopearl-Bug1 650 M chromatography resolved POD into four cationic fractions. Chromatography of wheat germ extract on CM-Sepharose isolated an anionic and a neutral @action. Following chromatography on Concanavalin-A Sepharose, enzymes from both cereals showed diferences in their elution properties. Optimum pH ranges were 4.0 to 5.5 (barley) and 5.3 to > 6.3 (wheat germ) and POD reacted differently under acidic or basic conditions. Their catalytic behavior in the presence of calcium also differed. Kinetics of POD were of Michaelian type with a ping-pong mechanism and Michaelis constants of guaiacol oxidation in the presence of hydrogen peroxide variedfrom one enzymatic group to another.

The three genes pduCDE encoding the diol dehydratase of Lactobacillus collinoides, have been cloned for overexpression in the pQE30 vector. Although the three subunits of the protein were highly induced, no activity was detected in cell extracts. The enzyme was therefore purified to near homogeneity by ammonium sulfate precipitation and gel filtration chromatography. In fractions showing diol dehydratase activity, three main bands were present after SDS/PAGE with molecular masses of 63, 28 and 22 kDa, respectively. They were identified by mass spectrometry to correspond to the large, medium and small subunits of the dehydratase encoded by the pduC, pduD and pduE genes, respectively. The molecular mass of the native complex was estimated to 207 kDa in accordance with the calculated molecular masses deduced from the pduC, D, E genes (61, 24.7 and 19,1 kDa, respectively) and a a 2 b 2 c 2 composition. The K m for the three main substrates were 1.6 mM for 1,2-propanediol, 5.5 mM for 1,2-ethanediol and 8.3 mM for glycerol. The enzyme required the adenosylcobalamin coenzyme for catalytic activity and the K m for the cofactor was 8 lM. Inactivation of the enzyme was observed by both glycerol and cyanocobalamin. The optimal reaction conditions of the enzyme were pH 8.75 and 37°C. Activity was inhibited by sodium and calcium ions and to a lesser extent by magnesium. A fourth band at 59 kDa copurified with the diol dehydratase and was identified as the propionaldehyde dehydrogenase enzyme, another protein involved in the 1,2-propanediol metabolism pathway.

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