Transcarboxylase. 8. Isolation and properties of a biotin-carboxyl carrier protein.

Methylmalonyl CoA-oxalacetate transcarboxylase (EC 2. 1. 3. 1) from Propionibacterium shermanii is a biotin enzyme of 670,000 molecular weight containing 6 moles of biotin per mole of enzyme. The active enzyme dissociates spontaneously at low ionic strength and alkaline pH to a mixture of inactive subunits. One type of subunit contains all the biotin of the original molecule. The biotin unit has an S(20,w) = 1.3S and a molecular weight of approximately 12,000. It contains 1 mole of biotin and 1 half-cystine per mole. Qualitative dansyl techniques indicate that alanine is the amino terminal residue of the biotin subunit.