グリコチアミン水解細菌酵素

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A strain of Gram-positive coccus was isolated from soil which could grow on agar medium containing glycocyamine as single C and N source. The bacteria obtained, when cultivated on this medium, the ability to hydrolyze glycocyamine into glycine and urea. Urease was also present. Activity of the enzyme, glycocyamase, was determined by photometric estimation of the decreasing amount of the Sakaguchi-reaction positive substrate. Optimum pH was 7.0. Experimental temperature was 37℃ and test solutions, in which the final concentration of glycocyamine or other substrates was M/1000, were overlayed with toluene. Glycocyamase is thermostable and its action remained intact after heating the bacterial suspension at 55℃ for 30 minutes. The suspension of the bacteria thus adapted was not able to hydrolyse arginine, and α-guanido propionic acid, but arginic acid and β-guanido propionic acid though to a small extent, whereas the extract by M/10 Na_2 HPO_4(pH 9.0) of the acetone-dried bacteria hydrolyzed only glycocyamine and was inactive upon the other guanido compounds. The action of glycocyamase is therefore very specific. Moreover, the suspension did not produce any urea or ammonia from creatine and creatinine. However, it was observed that the Jaffe reaction of the test solution incubated with creatine became intensified and that with creatinine was on the contrary lessened. This indicates that the bacteria contain the creatinomutase which catalyses the mutual conversion of creatine and creatinine. Another enzyme, glycocyamidinase, which splits glycocyamidine to glycocyamine, and was previously investigated in this department, was also present, since the bacterial suspension lessened the Jaffe reaction of the test solution incubated with glycocyamidine. Therefore, the bacteria grown on glycocyamine medium contained glycocyaxnase, creatinomutase and glycocyamidinase. Whenthe bacteria were, however, transferred from the glycocyamine medium to an agar glycine medium, which contained as C and N source only glycine, and harvested on this, glycocyamase activity of the bacteria disappeared, but creatinomutase and glycocyamidinase existed as before. The action of glycocyamidinase was certified beside by Jaffe reaction also by measuring the increased extinction of the solution colored with the Sakaguchi's reagents. On the other hand, when the bacteria were transferredand grown on an agar creatine medium, an adaptive enzyme system which decomposes creatine and creatinine into urea and sarcosine was produced, as in the case of the bacteria previously investigated here in respect to creatinomutase. Glycocyamase was, however, absent. Heating of this bacterial suspension at 55℃ for 30 minutes abolished the enzyme action to produce urea from creatine and creatinine, whereas the creatinomutase and glycocyamidinase actions were ascertained to have remained. From above mentioned data it is clear, so far as the strain of soil bacteria isolated this time is concerned, that the glycocyamase is an adaptive enzyme, but creatinomutase and glycocyamidinase belong to the constitutive enzyme. It was observed previously at the investigation on the bacterial decomposition of creatine and creatinine that in a strain of soil bacteria grown on the creatine or creatinine agar medium an adaptive enzyme system was formed. Among the enzymes there were the creatinase which produces urea from creatine but not from glycocyamine and the creatinomutase, which accelerates reversible interchange of creatine and creatinine. It was remarkable, thereby, that by the same bacterial preparation glycocyamidine could be hydrolyzed to glycocyamine. From this fact a provisional assumption was made that through relative adaptation of the bacteria the glycocyamidinase might be formed hand in hand with the creatinomutase owing to the resemblance of chemical constitution of both substrates. However, the experiment described in the present paper shows that the creatinomutase and glycocyamidinase can be present together a priori as constitutive enzymes. Therefore, the relative adaptation theory should be reserved as not established for a time until some further studies will determine whether or not the two enzyme actions would be found dissociated in some other bacteria.
千葉大学の論文
1955-01-28

著者

中村彰
千葉大学医学部医化学教室

グリコチアミン水解細菌酵素

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