C-Terminal Propeptide of BKA has a Protease Sensitive Structure Without any Inhibitory Effect on BKA

In our previous study, we compared the two α-amylase enzymes from Bacillus sp.KR8104, BKA∆(N44) and BKA∆(N44C193) which is the secreted form of it. The results indicated that the presence of 193 amino acids propeptide in the C-terminal of BKA∆(N44) changed its enzymatic parameters like an uncompetitive inhibitor in comparison to BKA∆(N44C193). In the present study, we cloned the DNA sequence of BKA∆(N44) which codes the 193 amino acids propeptide in its C-terminal and the effect of this fragment as an inhibitor on BKA∆(N44C193) was investigated. We also studied the possible foldase activity of the propeptide in BKA∆(N44C193). Protease sensitivity of C-terminal 193 amino acid propeptide, BKA∆(N44) and BKA∆(N44C193) was compared in order to explain why  BKA∆(N44C193) is the only secreted form of α-amylase in the culture medium of Bacillus sp.KR8104. Circular dichroism indicated that the secondary structure of the C-terminal is mostly beta sheeted. At the end we proposed a possible regulatory role for the C-terminal propeptide of BKA.