Keratinases from pseudomonas aeruginosa KS-1: Characterization and degradation of surrogate prion protein Sup 35NM

Abstract

Keratinases are a special group of proteases which are well recognized for their action newlineon recalcitrant proteins such as feather, nail, hair, hoof etc. They are lately being recognized newlineas potential catalysts for degradation of prion. Few keratinases have already been newlinedocumented to degrade prion however treatment of the infected tissue with harsh alkali or at newlinehigh temperature is required. This limits the applicability of these enzymes. Thus, the need of newlinethe hour is to search for efficient keratinases which can degrade prion under ambient newlineconditions. newlineLooking into the above, the present investigation was undertaken to search for a newlinepotential prion degrading keratinase. Fifty feather degrading bacterial isolates were screened, newlineout of which eleven were selected as they could degrade chicken feather within 48 h. Among newlinethese, extracellular broth of nine isolates carried out cell free feather degradation. Isolate KS- newline1 which maximally degraded Sup 35NM was finally selected for further studies. It was newlineidentified as Pseudomonas aeruginosa and deposited to MTCC under the accession number newline10775. newlineTwo keratinases, KP1 and KP2 of 45kDa and 33kDa respectively were purified from newlineits extracellular broth. Keratinase KP1 shared homology with putative aminopeptidase while newlinekeratinase KP2 gave homology with pseudolysin. Keratinase KP1 was alkaline, serine, metal newlineactivated protease and KP2 was a neutral, thiol-activated, serine protease. Both the enzymes newlinewere extremely thermostable. K:C (keratinolytic: caseinolytic) ratio of 2.5 and 0.9 for KP1 newlineand KP2 respectively. Both also efficiently hydrolyzed p-nitroanilides with best activity on newlineN-Suc-Ala-Ala-Pro-Phe-pNA. They had unique activity on the synthetic substrate of plasmin. newlineHydrolysis of insulin B chain revealed KP1 and KP2 to have four and six cleavage sites newlinerespectively. newlineBoth the keratinases were constitutively expressed as extracellular proteins using newlinepEZZ18-E. coli HB101 system. Biochemical characterization the pH and temperature optima newlineof rKP1 and rKP2 to be pH 10.0/60oC