Coniferyl alcohol oxidase (CAO), a catechol oxidase (o-diphenol:oxygen oxidoreductase, E.C.1.10.3.1) specifically associated with lignification during wood formation in conifers, is described and its activity is compared with that of peroxidase. CAO activity is not affected by provision of H2O2, and although CAO is an O2-requiring enzyme able to oxidize substrates in common with laccase, CAO is distinct from laccase in catalytic rate, amino acid composition, response to effectors, copper content and type, protein size, and immunodetectability. Peroxidase activity, readily detected in phloem, cambium and xylem, was inversely correlated with lignification. In contrast, CAO activity was restricted to the lignifying zone. Peroxide and superoxide anion were found in the phloem and cambial zone, respectively, but a pool of H2O2 in support of lignification could not be detected in lignifying xylem or elsewhere. Additional evidence has indicated that coniferin hydrolysis may be the rate limiting step in the supply of coniferyl alcohol for oxidation by CAO.
Gišogenesis, otherwise known as secondary-xylem development, was investigated in an old-growth upland population of white spruce (Picea glauca (Moench) Voss) trees having morphologically diverse crowns and growing on a south slope north of East Fork Creek bordering never-glaciated Yukon Beringia. After tree felling, trunks were segmented into one-metre lengths. In the laboratory, widths of xylem layers were measured across the four cardinal directions at each height, followed by Pearson’s product momentum correlations to evaluate variation in historical gišogenetic vigour within and between trees. Substantial variation was found, and it cannot readily be explained in terms of differences in extrinsic environment. Physiological differences in intrinsic gišogenetic regulation within a genetically diverse population, comprising both refugia and recent recruits, is proposed as a probable explanation, thus emphasizing the individuality of each tree’s internal control over how it responds to the extrinsic environment. Further investigations within Yukon Beringia may yield insight into evolutionary diversification of gišogenesis.
Alkali-insoluble cellulose and water-soluble polysaccharide production by wild-type Acetobacter xylinum colony and liquid cultures was investigated. The mass of cellulose exceeded that of soluble polysaccharides in liquid cultures while the reverse situation occurred in colony cultures. The soluble polysaccharide fraction, 3 × 10 5 to 5 × 10 5 in molecular weight, was found by DEAE-Sephacel chromatography to be a complex of several acidic, nitrogenfree polysaccharides. One acidic polysaccharide was predominant in the complex, and gas–liquid chromatography and mass spectrometry showed this to contain glucose, rhamnose, mannose, and glucuronic acid in molar ratio of 6:1:1:1, respectively. 13 C and 1 H nuclear magnetic resonance spectra are presented for this major polysaccharide component. Several minor, soluble, acidic polysaccharides were related in chemical composition to the major soluble polymer. The relation of these soluble polysaccharides to cellulose biogenesis is discussed.
