The importance of threonine-301 from cytochromes P-450 (laurate (ω-1)-hydroxylase and testosterone 16α-hydroxylase) in substrate binding as demonstrated by site-directed mutagenesis

AbstractThreonine-301 from rabbit liver cytochromes P-450 (laurate (ω-1)-hydroxylase and testosterone 16α-hydroxylase) has been replaced by histidine via site-directed mutagenesis. In the oxidized state the mutant P-450s exhibited typical low-spin type absorption spectra of P-450 and their reduced CO complexes showed a Soret peak at 450 nm. However, no spectral change was induced on addition of substrates for their wild-type counterparts. The mutant P-450s were also completely devoid of the hydroxylase activity. These findings suggest that threonine-301, which is highly conserved in P-450s and located at the distal heme surface, plays an important role in substrate binding

STUDY OF AN ORGANIC CRYSTALLIZATION FOULING PROBLEM

One of the aromatic compound plants in Mitsubishi Chemical Corporation has a heavy crystallization fouling problem. We have been studying the crystallization process using the shell and tube heat-exchanger. In order to solve our fouling problem of the heat exchanger, we developed the specified evaluation equipment (crystallization fouling simulator : CFS) which consists of a single tube heatexchanger (Tube size: ID=10.3mm Length=500mm). The result of the modeling for describing the crystallization fouling rate and the countermeasure of the fouling problem are discussed in this work. It can be possible to describe the fouling rate as one equation which has two parameters, and the fouling rate of the industrial plant and the evaluation equipment agree with each other