Catalyzes two activities which are involved in the adenosylcobalamin biosynthesis: decarboxylates L-threonine-O-3-phosphate to yield (R)-1-amino-2-propanol O-2-phosphate, the precursor for the linkage between the nucleotide loop and the corrin ring in cobalamin, and catalyzes amidations at positions B, D, E, and G on adenosylcobyrinic A,C-diamide. NH(2) groups are provided by glutamine, and one molecule of ATP is hydrogenolyzed for each amidation (By similarity). H(+) + O-phospho-L-threonine = (R)-1-aminopropan-2-yl phosphate + CO2 Cofactor biosynthesis; adenosylcobalamin biosynthesis. In the N-terminal section; belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family. In the C-terminal section; belongs to the CobB/CobQ family. CobQ subfamily.