Enzymes from Cold-Adapted Microorganisms. The Class C Beta-Lactamase from the Antarctic Psychrophile Psychrobacter Immobilis A5

in European Journal of Biochemistry (1997), 244(1), 186-91

A heat-labile beta-lactamase has been purified from culture supernatants of Psychrobacter immobilis A5 grown at 4 degrees C and the corresponding chromosomal ampC gene has been cloned and sequenced. All ... [more ▼]

A heat-labile beta-lactamase has been purified from culture supernatants of Psychrobacter immobilis A5 grown at 4 degrees C and the corresponding chromosomal ampC gene has been cloned and sequenced. All structural and kinetic properties clearly relate this enzyme to class C beta-lactamases. The kinetic parameters of P. immobilis beta-lactamase for the hydrolysis of some beta-lactam antibiotics are in the same range as the values recorded for the highly specialized cephalosporinases from pathogenic mesophilic bacteria. By contrast, the enzyme displays a low apparent optimum temperature of activity and a reduced thermal stability. Structural factors responsible for the latter property were analysed from the three-dimensional structure built by homology modelling. The deletion of proline residues in loops, the low number of arginine-mediated H-bonds and aromatic-aromatic interactions, the lower global hydrophobicity and the improved solvent interactions through additional surface acidic residues appear to be the main determinants of the enzyme flexibility. [less ▲]

TEMPERATURE-DEPENDENCE OF GROWTH, ENZYME-SECRETION AND ACTIVITY OF PSYCHROPHILIC ANTARCTIC BACTERIA

in Applied Microbiology & Biotechnology (1994), 41(4), 477-479

Five psychrophilic Antarctic bacteria have been selected for their capacity to secrete exoenzymes into culture medium. These strains are able to grow from 0 to about 25 degrees C. However, production of ... [more ▼]

Five psychrophilic Antarctic bacteria have been selected for their capacity to secrete exoenzymes into culture medium. These strains are able to grow from 0 to about 25 degrees C. However, production of lipase from Moraxella, alpha-amylase from Alteromonas haloplanctis, beta-lactamase from Psychrobacter immobilis and protease from Bacillus is maximal at temperatures close to that of their environment (-2 to 4 degrees C) and is strongly inhibited at higher temperatures. This thermal effect involves alterations in the secretory pathway in the upper range of temperatures, losses due to the enzyme thermal lability and in some cases to reduction in cell development. The apparent optimal activity temperature of these enzymes is between 30 and 40 degrees C, i.e. about 20 degrees C lower than that of their mesophilic counterparts. [less ▲]