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Stimulation by Calcium of the Formation of Active Extracellular Proteinase by Pseudomonas fluorescens spp.¹

Food Research Institute, Research Branch, Agriculture Canada, Ottawa, Canada K1A 0C6

ABSTRACT

Pseudomonas fluorescens produced extracellular proteinase in mineral salts medium in response to the addition of small molecular weight compounds derived from skim milk. Further fractionation of these compounds on Sephadex G-10 gave a highly stimulatory fraction lacking in peptides or amino acids but high in calcium. Further studies showed that proteinase production in mineral salts medium containing calcium was 29 to 64% of that in skim milk. Zinc, manganese, and magnesium ions failed to substitute for calcium. At 20 and 5°C, 50 and 10 µM calcium, respectively, were required for half maximum synthesis. Several complex media supported variable growth and enzyme synthesis; however, this variability did not seem related to the calcium content of the medium. Calcium was required for the formation of active extracellular proteinase by a number of strains of Pseudomonas fluorescens when growing in mineral salts medium. These results suggest that milk proteins are not essential for proteinase synthesis by Pseudomonas fluorescens.

¹ Contribution Number 599 from the Food Research Institute.