engleski

Aminopeptidases in mycelium and growth medium of Streptomyces rimosus strains

In mycelia and culture filtrate of Streptomyces rimosus aminopeptidases (APs) of the same substrate specificities were detected. To compare extracellular and intracellular prolyl-, leucyl- and arginyl-AP, dynamics of their biosynthesis, excretion and localization were analyzed during submerged cultivation of two S. rimosus strains, T55 and ZGL3, in several media. APs activity in mycelia reached maximum in stationary phase, and decreased to the different extent afterwards. APs accumulation in culture filtrate, when peptide richer medium was used, followed growth and decreased later on, except Pro-AP. When S. rimosus was grown in glucose richer medium, accumulation of APs in the medium started at the late log phase and continued to the end of cultivation, due to cell lysis. Combined addition of calcium and ammonium salts to tryptone-soy-broth medium increased APs activity in ZGL3 culture filtrates up to two times. The APs intracellular activity was significantly higher compared to its intercellular activity (2 to 24 times). Mycelium/medium APs activity ratio decreased with age of the culture, its change being dependent on the S. rimosus strain, growth medium composition and APs specificity. Leu-AP was the most prone to be released from the mycelium suggesting that part of the enzyme could be excreted by active transport. Determination of APs distribution within cell compartments has confirmed that the three APs are intracellular enzymes residing in cytosol, but also suggested their partial association with cytoplasmic membrane.

prolyl-; leucyl-; arginyl- aminopeptidases; localization; Streptomyces rimosus

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