UNUSUAL EFFECT OF HIGH HYDROSTATIC-PRESSURE ON BASIC PHOSPHOLIPASE A(2) FROM VENOM OF AGKISTRODON-HALYS-PALLAS

The pressure effect on basic phospholipase Az (BPLA(2)) from the venom of Agkistrodon Halys Pallas from the Zhe-Jiang province of China, was studied by fluorescence spectroscopy from 0.1 to 650 MPa. It was foun d that the pressure effect on the tryptophan residue fluorescence emis sion spectra of the enzyme were-was significantly different in two pre ssure ranges: from 0.1 to 400 MPa and from 400 to 650 MPa respectively . For increasing pressure, the spectruam shifted to the red in the low er pressure range and to the blue in the higher pressure range. Wherea s the red shift could be ascribed to the intrinsic pressure dependence of the fluorophore (trp), the blue shift indicated a pressure induced protein conformational change toward a structure where the single try ptophan is in a less polar environment, suggesting its burying deeper inside the protein. This is the first time that such a phenomenon has been observed. Generally, high pressure denaturation of proteins leads to a red shift of tryptophan fluorescence. It was also found that the break point in pressure at which the blue shift began was dependent b oth on temperature and on the presence of Ca++ ion, but not on the pro tein concentration. Experiments at different BPLA2 concentrations and light scattering under pressure indicated that the blue shift was not caused by protein aggregation under high pressure. (C) 1998 Academic P ress.