1. Protein-bound compound, protein-SS-C₃H₇ (III) formed by the reaction of egg albumin and C₃H₇SSC₃H₇ (I) or C₃H₇SSOC₃H₇ (II) as well as S-propylmercapto-L-cysteine (IV), reacts with thiamine to form thiamine propyl disulfide (TPD), whereby thiamine was masked.
2. The thiamine-masking reaction of III and IV did not proceed stoichiometrically as II; the masking activity of III was 15% of that of II and that of IV about 40%. On the contrary, I had scarcely any activity.
3. The thiamine-masking rate of III was about the same, whether it was produced from. I or II. The masking activity was dependent on the amount of C₃H₇SH bound with the protein.
4. It was confirmed that the thiamine-masking activity was increased with the rise in the concentration of either III (or IV) or thiamine, suggesting the existence of chemical equilibrium.
5. From the above findings the thiamine-masking activity of III or IV is considered to be due to the thiol disulfide exchange reaction between the thiol form of thiamine and these disulfides.

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1. Heterogeneity of malate dehydrogenase (MDH) activities was proved by electrophoresis on cellulose acetate of rat and human tissue homogenates. Two or more separable forms of MDH activities were found in these tissues. Each tissue exhibited a similar distribution of MDH activities.
2. The supernatant MDH showed a band of relatively less cathodic mobility (MDH 1), but the mitochondrial MDH (MDH 2) was found to be far more mobile, migrating toward the cathode. However, two MDH bands were observed in both fractions.
3. The acetone powder extracts showed also the two MDH activities.
4. The enzymes isolated from rat liver extracts were easely inhibited by heating, trypsin and oxaloacetate according to the staining methods.
5. It was concluded that the increased serum MDH following experimental liver damage in rats is mainly the form of MDH 1.

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1. The influence of the presence of α-tocophergl acetate (α-TAc) in the diet of rats on the latent ATP-ase activity, and the dinitrophenol (DNP)-induced activity has been investigated in isolated liver mitochondria.
2. The findings that α-TAc caused an increase in the latent activity of the enzyme but an inhibition of the degree of DNP-induced activity was investigated secondarily using whole rat liver homogenates and adding α-TAc in vitro.
3. α-TAc, when added to homogenate system, activates the latent ATP-ase activity, and inhibits the degree of DNP-stimulated activity, thus confirming the findings in isolated mitochondrial experiments.
4. It is concluded that α-TAc has at least two functions which result in paradoxical effects (a), in which ATP-ase is stimulated indirectly, possibly by a removal of free thiol groups which are inhibitory to ATP-ase, and (b) in which DNP is inhibited by complexing or by removal by some other means from the active bond site.

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1. The effects of various thiamine derivatives on the oxygen uptake were investigated by Peters' Catatorulin method, using the slices and homogenates of avitaminous pigeon brain.
2. In the experiment with the slices, thiamine propyl disulfide (TPD), thiamine tetrahydrofurfuryl disulfide (TTFD), thiamine-8-(methyl-6-acetyldihydrothioctate) disulfide (TATD) and thiamine disulfide (TDS) were more effective than thiamine in the oxygen uptake. S-carbalkoxy-thiamine (CAT) was less effective than thiamine. Thiamine diphosphate (TDP) and S-benzoylthiamine O-monophosphate (BTMP) had little effect. These differences seem to be caused by different cell permeability of each derivative.
3. In the experiment with the homogenates, TDP markedly stimulated the oxidation of pyruvate, and the other derivatives showed slight stimulation as thiamine.
4. A slight inhibition of the effect was noted in slices and homogenates by highly concentrated TPD and TATD, whereas it was not the case with concentrated TDS.
5. TDS seems to be the most effective compound to the avitaminous pigeon brain.

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1. The production of 5, 6-dimethylbenzimidazolylcobamide coenzyme from hydroxocobalamin or cyanocobalamin was studied using washed cell suspensions of Pr. shermanii. Under the experimental conditions almost complete conversion of hydroxocobalamin to the coenzyme was achieved at a concentration as high as 50μg/ml, which was about 10 times higher than that of the growing culture method reported previously.
2. As the concentration of the precursor increased, the degree of the transformation decreased and the formation of an unidentified vitamin B₁₂ analogue was observed. The availability of cyanocobalamin as the precursor was only one-third of that of hydroxocobalamin in this procedure.
3. The utilization of the distillage of acetone-butanol fermentation broth was studied as a substitute for the yeast extract contained in the culture medium. The replacement of the half volume of the tap water with the distillage supported the bacterial growth nearly to the same degree as that in Bernhauer's medium.
4. The employment of a solid culture method shortened the incubation time of a liquid culture method by 5 days.

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1. The difference was not observed in the effectiveness of hydroxocobalamin (OH-B₁₂) and cyanocobalamin (CN-B₁₂) as the precursor of 5, 6-dimethylbenzimidazolyl cobamide coenzyme (DBCC) by growing culture of Pr. shermanii cultivated for 8 to 10 days at 30°. But when DBCC was produced by the incubation of the precursor with washed cell suspension of the bacterium for 20 hours at 30°, OH-B₁₂ was quantitatively converted to DBCC, whereas CN-B₁₂, for the most past, remained unchanged.
2. The cause of the low conversion rate of CN-B₁₂ would be attributed to the small permeability or the less facility of transformation to DBCC or the combined effect of the two. In order to study this problem Pr. shermanii was cultivated for 9 days at 30° in the medium to which CN-B₁₂ or OH-B₁₂ had been added from the beginning of the culitivation or at an appropriate time in the incubation period and the amount and the form of the vitamin B₁₂ in the bacterial cells were investigated.
3. In the case of OH-B₁₂ most of the vitamin exogenously added on the 8th day was incorporated into the cells and transformed to DBCC as well as that added from the beginning of the incubation. On the other hand, the incorpoparion of CN-B₁₂ was lowered as the time of the addition was delayed.
4. In the cells grown in the presence of CN-B₁₂, only CN-B₁₂ and DBCC were detected and the presence of OH-B₁₂ was not ascertained. The fact may indicate that CN-B₁₂ is directly transformed to DBCC without changing to OH-B₁₂ or even if CN-B₁₂ is changed to OH-B₁₂, as an intermediate of the coenzyme, OH-B₁₂ would be immediately converted to DBCC.
5. From the results of this study it is not possible to conclude whether the formation of DBCC from CN-B₁₂ proceeds through OH-B₁₂ or not. However, it seems appropriate to conclude that either affinity to the bacterial cells or the conversion rate to DBCC of CN-B₁₂ is smaller than those of OH-B₁₂. It appears likely that the difference in the behaviors of OH-B₁₂ and CN-B₁₂ against bacterial cells is analogous to that against animal tissues.

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1. The best condition for the biosynthesis of biotin from desthiobiotin by the washed cells of Saccharomyces cerevisiae was found as follows: The cells cultured in a liquid medium containing a suboptimal amount (20mμg per 100ml) of DL-desthiobiotin for 1 to 3 days were incubated in the reaction mixture containing DL-desthiobiotin (2×10^-7 M) and glucose at 37° without shaking.
2. Sulfur necessary for the biosynthesis of biotin seems to be sufficiently present in the cells, because the addition of several sulfur compounds did not increase the formation of biotin. The synthesized vitamin was practically restricted in the cells and 87 per cent of it was present in a bound form.

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1. The cells cultured in the desthiobiotin-limitting and sulfur-deficient medium showed the marked ability of biotin formation from desthiobiotin and various sulfur sources.
2. The most effective sulfur compounds were metionine sulfoxide and methionine, followed by sodium sulfide, sodium, sulfite, sodium sulfate, homocysteine, S-adenosylmethionine, and methylmercaptan. Cysteine, cystine, methionine sulfone, 5′-methyladenosine, choline sulfate and glutathione were less effective. In the case of sodium sulfate, further addition of glucose in combination with desthiobiotin was necessary after preincubation, but not necessary in the case of methionine.
3. Biotin formation by biotin-deficient cell suspension was inhibited by ethionine and was restored only by addition of methionine.

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1. The biosynthesis of biotin-S³⁵ from H₂S³⁵O₄ and desthiobiotin by the washed cell suspension of biotin and sulfur-deficient Saccharomyces cerevisiae was investigated with the following two methods.
2. The biotin and sulfur-deficient cell suspension was incubated with sulfate-S³⁵ and D-glucose, and the fate of sulfate-S³⁵ was investigated. L-Methionine-S³⁵ was found to be produced predominantly.
3. The experiments with L-methionine-S³⁵ and desthiobiotin showed the formation of biotin-S³⁵ in a good yield.
4. Using 140μc of L-methionine-S³⁵, 0.26μc of biotin-S³⁵ was obtained by the biotin-avidin complex method, followed by autoradiography, bioautography and paper chromatoscanning.
5. From these findings, it is concluded that 70 per cent of the radioactivity in the biotin concentrate is located in biotin-related compounds, i.e., biotin-D-sulfoxide, biotin-L-sulfoxide, biocytin and biocytin sulfoxide.

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The inhibitory effects of 2-methyl-4-amino-5-hydroxymethylpyrimidine (OMPm) to pyridoxal for the growth of lactic acid bacteria, Leuconostoc mesenteroides P-60 and Streptococcus faecalis R, appeared to be relatively similar ratio at different levels of pyridoxal in the medium.
Among 21 OMPm derivatives, 2-methyl-4-methylamino-5-hydroxymethylpyrimidine had the highest activity (3-19 times as active as OMPm) as an inhibitor of pyridoxal for the growth of Leuc. mesenteroides and S. faecalis. 2-Methyl-4-amino-5-mercaptomethylpyrimidine itself showed some inhibitory activity (about 1 or 2 per cent that of OMPm).

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