초록
E. coli에서 ribosyl-HTP(hydroxytriamino pyrimidine)를 GTP로 부터 합성하는 효소 GTP cyclohydrolase II가 발견된 뒤 riboflavin의 ribityl group이 guanine nucleotide의 ribosyl group에서 직접 유래한다는 가설이 제안되었다. 본 연구에서는$(U- ^{14}C)$ guanosine을 media에 첨가하여 배양한 riboflavin overproducer 균주 Ashybya 에서 추출 정제한 riboflavin과 RNA에 각각 Incorporate된 guanosine label의 specific radioactivity를 비교 측정함으 로써 ribity I group 이 guanosine에서 기훤한다는 결과를 얻을 수 있었다. 이는 GTP cyclohydrolase II가 riboflavin 생합성의 초기 단계에서 직접 관여한다는 가설을 지지해 주는 것이다.
In order to investigate the origin of the ribityl froup of riboflavin and the involvement of GTP cyclohydrolase II in the riboflavin pathway, we studied the incorporation of $^{14}C-labeled$ guanosine using a well known riboflavin over producer, Ashbya gossypii.Cells were grown in a media containing $(U- ^{14}C)$ guanosine and the riboflavin and GMP were isolated and purifired by column chromatography. The isolated compounds, riboflavin and GMP were labeled in the ribityl and ribosyl side chain and the isoalloxazine and guannine moiety. By comparing the specific radioactivity of each compound we reached a conclusion that the ribose of guanosine is converted directly to the rivityl moiety of riboflavin. The results indicate that biosynthesis of the vitamin begins at the level of a guanosine compound and also suppory the involvement of GTP cyclohydrolase II in one of the early steps in the biosynthetic pathway.