Abstract
To find applicability of assay procedures of lathosterol 5-desaturase in rat liver microsomes to measurement of the enzyme activity in mouse skin, the enzyme reaction was examined using [^3H] labeled lathosterol. Specific activity of the enzyme thus measured was identical with that measured by the spectro-photometric method. Thus the spectrophotometric method can be used for the assay of lathosterol 5-desaturase in the skin microsomes. On the other hand, spectrophotometric method may also be used for the assay of provitamin D_3 7-reductase in the liver microsomes, where the method monitors the decrease of provitamin D_3. However, this method may not be applicable to the assay of the enzyme in the skin because of high contents of provitamin D_3 and low specific activity of the enzyme in the skin microsomes.
