The central carbon metabolism is well investigated in bacteria, but this is not the case for archaea. MJ0400-His(6) from Methanocaldococcus jannaschii catalyzes the cleavage of fructose-1,6-bisphosphate (FBP) to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate with a V(max) of 33 mU mg(-1) and a K(m) of 430 microM at 50 degrees C. MJ0400-His(6) is inhibited competitively by erythrose-4-phosphate with a K(i) of 380 microM and displays heat stability with a half-life of c. 1 h at 100 degrees C. Hence, MJ0400 is the second gene encoding for an FBP aldolase in M. jannaschii. Previously, MJ0400 was shown to act as an 2-amino-3,7-dideoxy-D-threo-hept-6-ulosonic acid synthase. This indicates that MJ0400 is involved in both the carbon metabolism and the shikimate pathway in M. jannaschii.