The Action of Streptomycins on the Chloroplast System of Euglena gracilis

Five streptomycins bleached the chloroplast system of Euglena gracilis; the most effective were those which contained an aldehyde group in the streptose moiety: streptomycin and hydroxystreptomycin. Derivatives containing a secondary alcohol group in place of the aldehyde (dihydro-, dihydrodesoxy-, dihydrohydroxystreptomycin) require higher concentrations to elicit the same effect. Hydroxylamine reversed the bleaching effects of streptomycin and hydroxystreptomycin but not of dihydro-, dihydrodesoxy-or dihydrohydroxystreptomycin. These observations suggest that the aldehyde group of the streptomycins contributes to the action of these antibiotics on Euglena chloroplasts; the action of hydroxylamine would be to either remove the antibiotic from its site of action or to render it ineffective in vivo by reaction with the aldehyde group

The catalytic mechanism of cellulase

NRC publication: Ye

On the Mechanism of the Laccase-Mediator System in the Oxidation of Lignin

In an effort to elucidate the role of phenolic and non-phenolic lignin subunits in a laccase mediator (LM) system, vanillyl alcohol was oxidized with laccase in the presence and absence of the mediator 1-hydroxybenzotriazol (HBT). Furthermore, the role of phe- nolic, aliphatic hydroxyl, and carboxylic Introduction acid moieties in lignin degradation was elucidated by selectively blocking them. The modified samples were then sub- jected to laccase and laccase ± HBT treatments. On the basis of this data it was possible to establish the role of this mediator. HBT mediates the oxidation of lignin by inducing side-chain oxida- tion and oxygen-addition products rath- er than oxidative coupling reactions