The N-Terminal Sequence ofLactococcus lactisPhosphoglucose Isomerase Purified by Affinity Chromatography Differs from the Other Species

A specific monoclonal antibody, M3A, was produced to rapidly purifyLactococcus lactisphosphoglucose isomerase (PGI) for amino acid sequence analysis. M3A recognized theLac. lactisPGI specifically and sensitively with both enzyme-linked immunosorbent assay and Western blot analysis. The enzyme was rapidly purified to a specific activity of 21.8 U/mg with a yield of 20% by a three-step procedure, including M3A-bound Sepharose chromatography. The specific activity of PGI was increased about 64.1-fold from the cell lysate. The molecular mass ofLac. lactisPGI was estimated to be about 50 kDa by SDS–PAGE. The N-terminal amino acid sequence ofLac. lactisPGI exhibited no significant similarity to other PGIs, except for a 52.6% identity toBacillus stearothermophilusPGI A and PGI B. These results suggest that there might be some molecular types of PGI.