Absolute stereochemistry of leucinopine, a crown gall opine

Abstract Crown gall tumors incited by Agrobacterium tumefaciens strain Bo542 have been reported to synthesize a tumor-specific substance identified as N -(1,3-dicarboxypropyl)-leucine (leucinopine), a compound with two centers of asymmetry. We report here evidence that leucinopine is indeed a crown gall opine, in that it is specifically catabolized by A. tumefaciens strains carrying the tumor-inducing plasmid pTi Bo542, as well as strains carrying closely related plasmids pTi AT1 and pTi AT4. We further report catabolism of leucinopine by the succinamopine-type strains A518, A519 and A532, carrying pTi EU6, pTi AT181 and pTi T10/73, respectively. Strains lacking any virulence plasmid, as well as those carrying octopine or nopaline type Ti plasmids or mannopine type Ri plasmids, did not catabolize leucinopine. On the basis of specificity of catabolism by bacteria carrying pTi Bo542, we conclude that the stereochemistry of natural leucinopine is l -threo, i.e. l glu , l leu . Such stereochemistry is novel in the opines known thus far: octopine, nopaline and succinamopine have d , l -stereochemistry: d ala , l arg (octopine), d glu , l arg (nopaline) and d glu , l asn (succinamopine).