SECONDARY STRUCTURE OF SOME ASPARTYL PROTEINASES

Abstract

A structural study of some aspartyl proteinases was undertaken. Secondary structure prediction methods indicate that chymosin, pepsin, penicillopepsin and Mucor miehei proteinase have relatively high proportions of β-sheet with active site aspartic acid residues located in β-turn regions. Secondary structure determination from far-UV CD spectral data support the above finding that the aspartyl proteinases have a high proportion of β-sheet. The proportion of β-sheet generally decreased at pH values greater than 6.3. More extensive unfolding occurred with pepsin and penicillopepsin than chymosin, Mucor miehei proteinase, Mucor pusillus proteinase and Endothia parasitica proteinase in the neutral to alkaline pH range. Results obtained from the near-UV CD spectra of the aspartyl proteinases indicate a change in spectra in the neutral to alkaline pH range which suggests the importance of aromatic groups to tertiary structure stability.