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Communications to the Editor 1515 showed almost no activity as the amide donor.Under the conditions of the experiment shown in Table II, glutamine supply limits DPN synthesis.Thus, in a separate experiment under similar conditions, with NA held constant at 10 /¿moles per vessel, DPN synthesis in the presence of 0, 4, 10 and 20 µ of glutamine was 0.052, 0.104, 0.172 and 0.274 µ , respectively. Further investigations are in progress seeking to elucidate the mechanism of pyridine nucleotide synthesis from nicotinic acid and its amide.

Incubation of 17a-hydroxyprogesterone with Rhizopus arrhizus Fischer (A.T.C.C. 11145) produced in good yield 6&17adihydroxyprogesterone and in small amounts 1 I ~~~17a-dihydroxyprogesterone. Incubation with Rhizopiis nigricans Ehrh (.4 T C.C R22711) gave excellent yield4 of I 1 ol,17a-dihydrozyprogesterone and very little of 6@,17a-dihydroxyprogesterone DiscussionIn paper 111 of this series? we reported that Rhizopus arrhizus oxygenates desoxycorticosterone in good yield to 6P-hydroxy-1 l-desoxycorticosterone and produces only very small amounts of 11epicorticosterone.Incubation of desoxycorticosterone with Rhizopus nigricans gave 1 1-epicorticosterone in good yield.When the bioconversion of Reichstein's Compound S was investigated'" essentially the same results were obtained] inasmuch as 6i3117a,21-trihydroxy-.l-pregnene-3,20-dione and 1 laIl7a,21-trihydroxy-4-pregnene-3,20-dione (compound 11-epi F) were produced by Rhizopus arrhizus as well as by Rhizopus nigricans. In conformity with the previous experience Rhizopus nigricans performed 11oxygenation in higher yields than Rhizoeus arrhizus did. These results pointed to a significant difference between the oxygenation of progesterone in the one case and of desoxycorticosterone and Iieichstein's Compound S in the other. The introduction of one or more hydroxy groups into the side chain of the basic substrate molecule, Le., proges-

It is difficult for us to evaluate this report or compare results with ours since intermediate isomeric mixtures were not separated, and melting points of the crystalline products obtained in the attempted PGF synthesis were not given.

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