Comparative study on proteinase R, T, and K from Tritirachiam album limber

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Abstract
Proteinase R and T purified from Tritirachiam album limber were characterized in comparison with proteinase K using circular dichroism (CD), enzyme activity, thermal melting, and sodium dodecylsulfatc polyacrylamide gel electrophoresis (SDS‐PAGE). CD analysis suggested that these three proteins possess some β‐sheet structure, with little α‐helix except for proteinase R which showed about 14%α‐helix. SDS‐PAGE and gel filtration in 0.1% SDS indicated that proteinase T and K are resistant to SDS‐induced unfolding similar to subtilisin. Thermal denaturation experiments showed the melting temperature for proteinase T to be 67° and that for proteinase K to be 65° in the absence of Ca2+, with higher melting temperatures in the presence of Ca2+. However, the enzyme activities of proteinase T and R were significantly lower than those of proteinase K.