1. Field of the Invention
The present invention relates to a method for the biological preparation of 25-hydroxyvitamin D compounds and 1.alpha.,25-dihydroxyvitamin D compounds from vitamin D compounds.
2. Prior Art
Vitamin D compounds are known to be important vitamins which participate with absorption of calcium in the body and acceleration of calcium metabolism of the bone, and to be activated by hydroxylating at the 25-position in the liver and at the 1.alpha.-position in the kidney [H. F. DeLuca and H. K. Johns, in Ann. Rev. Biochem., vol. 52, page 411 (1983)]. However, patients with liver function disorders are deficient in production content of 25-hydroxyvitamin D.sub.3 in the body. Accordingly, administration of 25-hydroxyvitamin D.sub.3 to these patients is effective from the viewpoint of a supply of the vitamin deficiency in the body. Furthermore, 1.alpha.,25-dihydroxyvitamin D.sub.3 has especially strong activity, and shows remarkable effect on patients with renal failure from the same viewpoint as described above. It is known that 1.alpha.,25-dihydroxyvitamin D.sub.3 can be obtained from 25-hydroxyvitamin D.sub.3 as a material by biological and enzymatic chemical conversions (Japanese Patent Kokai 2-469 and ibid. 2-231089). Accordingly, it is industrially advantageous to prepare 25-hydroxyvitamin D.sub.3 and 1.alpha.,25-dihydroxyvitamin D.sub.3 inexpensively.
Direct introduction of hydroxyl groups into vitamin D.sub.3 compounds at the 1.alpha.- and/or 25-positions by organic synthesis is not known. Such an introduction by using animal organs is known [Biochem. Biophys. Res. Commun., vol. 36, page 251 (1969)], but, this method is not industrially practical. Hydroxylation of vitamin D.sub.3 at the 1.alpha.- and/or 25-positions by enzymatic chemistry using microorganisms was recently disclosed (Japanese Patent Kokai 2-469 and ibid. 2-231089).
According to the preparations of 25-hydroxyvitamin D compounds and 1.alpha.,25-dihydroxyvitamin D compounds by enzymatic chemistry using the microorganisms disclosed in Japanese Patent Kokai 2-469 and ibid. 2-231089, the ratio of conversion from the substrate vitamin D.sub.3 and 25-hydroxyvitamin D.sub.3 into 25-hydroxyvitamin D.sub.3 and 1.alpha.,25-dihydroxyvitamin D.sub.3, respectively, is not satisfactory. Furthermore, these methods have problems to solve for the industrial preparation, for example, since the concentration of the substrate used is low, these methods need large scale equipment for industrial production.
Thus, an object of the present invention is to provide an improved method for the biological preparation of 25-hydroxyvitamin D compounds and 1.alpha.,25-dihydroxyvitamin D compounds from vitamin D compounds and 25-hydroxyvitamin D compounds, respectively, using the prior art microorganisms or enzymes with remarkably increased conversion ratio.
As a result of earnest research in order to increase the ratio of conversion from vitamin D compounds and 25-hydroxyvitamin D compounds into 25-hydroxyvitamin D compounds and 1.alpha.,25-dihydroxyvitamin D compounds, respectively, by using microorganisms, the present inventors have found that the conversion ratio is remarkably increased by adding cyclodextrin compounds to a reaction mixture.