The 21-dehydroxylation of corticosteroids: evidence for an enol intermediate and the hydroxylation of steroids by fungal cyto-chrome P450: evidence for a stepwise mechanism

Two enzyme mechanisms were examined: the 21-dehydroxylation of corticosteroids by the anaerobe Eubacterium l en tum, and the hydroxylation of steroids by fungal cytochrome P450. Deuterium labelling techniques were used to study the enzymic dehydroxylation. Corticosteroids doubly labelled (2H) at the C-21 position were incubated with a culture of Eubacterium lentum. It was found that t he enzymic dehydroxylation proceeded with the loss of one 2H f rom C-21 per molecule of substrate. The kinetic isotope ef fect f or the reaction was found to be k~kD = 2. 28. These results suggest that enzyme/substr ate binding in this case may proceed via t he enol form of the substrate. Also , it appears that this binding is, at least in part, the rate determining step of t he reaction. The hydroxylation of steroids by fungal cytochrome P450 was examined by means of a product study. Steroids with a double bond at the A8 (9), ~( lO ), or ~ (ll) position were synthesized. These steroids were then incubated with fungal strains known to use a cytochrome P450 monooxygenase to hydroxylate at positions allylic to these doubl e bonds. The products formed in these incubations indicated that the double bonds had migrated during allylic hydroxylat ion. This suggests that a carbon centred radical or ion may be an intermediate i n the cytochrome P450 cat alytic cycle.

Mentorships and co-op placements as a means of heightening the need for a secondary school diploma to the education of at-risk students.--

Both educators and politicians appear to be quite concerned about a dropout rate in Ontario's public schools of some 30 percent. With the basic understanding that a high dropout rate is costly both in economic terms and in human terms, something quite obviously needs to be done to reduce the dropout rate in Ontario schools and, in doing so, ensuring Ontario and its graduates an active role in a growing global economy. This study is an exploratory pilot study in that it examined mentoring and the role that mentoring can play in assisting a student in staying in school and graduating from secondary school. Also incorporated in this is co-operative education and the role it can play, through mentoring, in making students aware of lifestyle level of employment, and of the skills necessary to obtain gainful, meaningful employment. In order to gain information on student attitudes, needs and expectations of a mentoring situation, a series of three questionnaires was used. Also, a questionnaire was distributed to the various co-operative education employers. The intent of this questionnaire was to probe the attitudes, needs and expectations of a mentoring situation from the perspective of an employer. The findings of this study indicated that co-operative education and mentoring are a very valuable and useful component in education. There exist certain factors in a co-operative education setting that serve to enhance and to augment the traditional or "theoretical" setting of the classroom. In addition, a mentoring situation tends to add a sense of relevance to education that students seem to require. Also, an opportunity is offered that allows a student to practice and further refine the skills that have been taught over the course of the student's academic life. Results from this study suggested that a mentoring situation, occurring through a co-operative education situation, adds relevance and a sense of "application" to the traditional or classroom schooling situation. The whole idea of mentoring bodes well for the future of education and of the student. Many advantages are identified in a mentoring situation. One of the advantages is that the schools are able to work quite closely with the community and business in order to stay current and informed on the needs and expected needs of the business community. Co-operative education has now gone beyond being an "experimental" mode of education. All students can benefit from being involved in the program. Certainly at-risk students are aided with staying in school. Those students who are said to be not at-risk can also benefit from being enrolled in the program by gaining hands-on work experience and some of the necessary skills to ensure a place in a growing world economy.