Table 1.

Purification of hMS

	Total protein, mg	Total activity, nmol/min	Specific activity, nmol·min−1·mg−1	Yield, %	Purification, n-fold
Crude extract	366	2,530	6.9	100	1
B12-affinity	0.47	823	1,750	32	253
Chitin beads	0.35	678	1,940	27	279

Six grams of wet Sf9 cells infected with recombinant baculovirus was used. MS activity was measured by using the aqCbl/DTT reducing system, as described in Materials and Methods. The activity in the crude insect cell extract, where MS is present as apoenzyme, was measured after incubation of the apoMS with 50 μM MeCbl for 15 min at 37°C to reconstitute holoMS.