EFFECT OF SELF-DEGRADATION PRODUCTS ON CRYSTALLIZATION OF PROTEASE THERMOLYSIN

The effect of self-degradation products of protease thermolysin on the crystallization of thermolysin was investigated. Crystallizations wer e carried out at the concentration of the self-degradation products of 0 to 0.622 mg/ml, 5-degrees-C and pH 7.0. The initial concentration o f thermolysin was constant (1.70 +/- 0.01 mg/ml). Crystallizations wer e monitored by dynamic light scattering and photomicroscopy. The cryst allization of thermolysin in the presence of the self-degradation prod ucts proceeded through two successive steps: the formation of primary particles and the formation of large crystals by the aggregation of th e primary particles. Low concentration of the self-degradation product s (0.212 mg/ml) accelerated the formation of the primary particles and also the formation of the large crystals. High concentration of the s elf-degradation products, however, inhibited the formation of the prim ary particles and their aggregation to the large crystals. As the resu lt, a large number of small aggregates which had not grown to the larg e crystals were observed by photomicroscopy. An analysis of the crysta ls and the primary particles formed in the presence of the self-degrad ation products by gel filtration high performance liquid chromatograph y revealed that the self-degradation products are not incorporated in the primary particles, but are incorporated probably in the openings b etween the primary particles during the crystallization.