lividans TK24/pNA-B3, and S. lividans TK24/pNA-B1B3 separately. The HPLC profile of the crude compounds isolated from S. lividans TK24/pNBS2 usually showed two major peaks at a retention time of 50.3 min (1b) and 26.6 min (1a). When compounds extracted from the S. lividans TK24/pNA-B1 strain were analyzed, the HPLC profile was found to be similar to that of S. lividans TK24/pNBS2 (Fig. 3a).
However, S. lividans TK24/pNA-B3 showed a distinct peak at a retention time of 16.5 min (2) and detected in negative mode by LC–MS ([M-H]−=217). While the peak detected at 26.6 min retained in this strain also, another peak at 50.3 min decreased (Fig. 3b). Interestingly, when an HPLC chromatogram from the extract GDC-0941 nmr of S. lividans TK24/pNA-B1B3 was analyzed, a dominant peak was detected at 12.5 min (Fig. 3c). Similarly, TLC analysis of the crude extracts from S. lividans TK24/pNA-B1B3 showed a distinct UV fluorescent spot (Rf=0.7), which was not observed in the crude extracts from S. lividans TK24/pIBR25, S. lividans TK24/pNBS2, S. lividans TK24/pNA-B3, and S. lividans TK24/pNA-B1. We purified the compound extracted from S.
lividans TK24/pNA-B1B3 by preparative TLC and the yield of the purified products was 6.3 mg L−1. The compound had 12.5-min retention time in HPLC. We observed the major peak of 231 [M-H]− of the corresponding compound by the LC–MS spectrometry analysis. Finally, the product was characterized by 1H NMR and 13C NMR spectroscopy (Table 3). At 3.68 p.p.m. for 1H NMR, we Regorafenib clinical trial found a singlet peak with 3H, it responses for O-methylation at C-7. Furthermore, it was confirmed by 13C NMR at 53.5 p.p.m. Thus,
from these analyses, we found our target product (3) from the extracts of S. lividans TK24/pNA-B1B3. Streptomyces carzinostaticus ATCC 15944 is a producer of a chromoprotein antitumor antibiotic, NCS. NA is one of the moieties of the NCS chromophore Endonuclease that binds to the NCS apoprotein to protect, carry, and deliver the drug to its DNA target. As the NA moiety of the NCS chromophore plays an important role, we were keenly interested to elucidate the complete biosynthesis of NA of the NCS chromophore. Among the four genes ncsB, ncsB1, ncsB2, and ncsB3 that were putatively assigned for the biosynthesis of NA moiety in the NCS chromophore, we characterized ncsB as NAS by heterologous expression in S. lividans TK24 in our previous study. In the study, heterologous expression of NAS in S. lividans TK24 resulted in the production of a major product 1a and a shunt product 1b. From these results, we assumed that O-methyltransferase gene ncsB1 might catalyze methylation at the hydroxyl group of C2 position of 1a or 1b and hydroxyl group containing methylene at C5 positions of 1b to yield new NA derivatives. In pursuit of such NCS derivatives, we expressed ncsB1 along with ncsB in S. lividans TK24 and analyzed the expected products, but we failed to obtain those products. Meanwhile, Luo et al.