The cleavage of β‐cyclodextrine by sodium periodate at the seven 2–3 diols of the glucose unit gives rise to the polyaldehyde 1, used to modify α‐amylase. The reductive modification of α‐amylase from Bacillus licheniformis reduced the number of reactive lysine groups from 8 to 3.5 per mol of enzyme with an activity loss of 25% and increased the half‐life at 80°C from 4.7 to 7.0 minutes.
The allelic state of relA influences the phenotype of Escherichia coli strains carrying the lysA22 mutation:lysA22 relA strains are Lys- where lysA22 relA+ strains grow (slowly) in the absence of lysine. This physiological effect has been related to an effect of the expression of the relA locus on the regulation of lysine biosynthesis. The fully derepressed levels of some lysine enzymes (aspartokinase III, aspartic semialdehyde dehydrogenase, didhydrodipicolinate reductase) are observed under lysine limitation only in rel+ strains. And the induction of DAP-decarboxylase by DAP is much higher in rel+ than in rel- strains when an amino acid limitation of growth is also realised. These results are in agreement with the hypothesis of Stephens et al. (1975) on a possible role of the stringent regulation as a general signal for amino acid deficiency.
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