aldehydo-D-galactose 6-phosphate = keto-D-tagatose 6-phosphate Carbohydrate metabolism; D-galactose 6-phosphate degradation; D-tagatose 6-phosphate from D-galactose 6-phosphate: step 1/1. Heteromultimeric protein consisting of LacA and LacB. By lactose or galactose. The operon consists of lacABCDFEGX. This gene was sequenced from pMG820, a laboratory-derived deletion of the naturally occurring plasmid pLP712. Belongs to the LacAB/RpiB family.