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Aminopeptidases in Mycelium and Growth Medium of Streptomyces rimosus Strains

Jasminka Špoljarić, Bojana Vukelić and Ljubinka Vitale*


Department of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička cesta 54, HR-10000 Zagreb, Croatia

Article history:

Received November 11, 2008
Accepted May 27, 2009

Key words:

prolyl, leucyl and arginyl aminopeptidases, localization, Streptomyces rimosus

Summary:

Aminopeptidases (APs) of the same substrate specificities have been detected in the mycelia and culture filtrate of Streptomyces rimosus. 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. AP activity in mycelia reached maximum in the stationary phase, and decreased to different extent at a later stage. The accumulation of APs, except prolyl aminopeptidase (ProAP), in the culture filtrate followed the growth of bacteria and decreased later on, when peptide-richer medium was used. When S. rimosus was grown in glucose- richer medium, the accumulation of APs in the medium started at the late log phase and continued to the end of cultivation, due to cell lysis. The combined addition of calcium and ammonium salts to tryptone soy broth increased the AP activity in S. rimosus ZGL3 culture filtrates up to two times. The AP intracellular activity was significantly higher compared to its intercellular activity (2 to 24 times). Mycelium/medium AP activity ratio decreased with the age of the culture, its change being dependent on the S. rimosus strain, growth medium composition and AP specificity. Leucyl AP (LeuAP) was the most prone to be released from the mycelium, suggesting that part of the enzyme could be excreted by active transport. Determination of AP 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.

 


*Corresponding author:           vitale@irb.hr
                                               ++385 1 4571 223
                                               ++358 1 4680 195

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