Part:BBa_K5443028:Experience

Some preliminary evidence for successful expression of at least the C3H-Sam5 enzyme in pMQ3A comes from the brown diffusible pigment produced by E.coli DH10B(pMQ3A) cultures expressing these genes (Fig. 1 - see plates in first column on left); we believe this is a melanin-like pigment made from 'accidental' hydroxylation of tyrosine, which yields L-DOPA, which polymerises. There is precedent for this brown pigment in studies of C3H-HpaBC here (BBa_K5443003) and elsewhere (BBa_K1124011); the E.coli HpaBC enzyme seems to be more active in making the pigment than the Saccharothrix Sam5 enzyme.

Figure 1. Transformation plates of plasmids into E.coli DH10B and RARE
Some plates show diffusion of a brown pigment from colonies into the surrounding agar, suggesting a side-reaction of the enzyme C3H that produces the brown pigment L-DOPA.