The patient group was restricted to patients with complete
apoenzyme deficiency (termed [mut.sup.0] in MMA).
The
apoenzyme stimulation tests for vitamin B1, B2 and B6 adapted to the Cobas Bio analyzer.
In brief, 0.2 mL each of holoenzyme (3.75 g/L) and
apoenzyme (1.0 g/L) was added to 0.2 mL of 0.8 mol/L perchloric acid.
These include loss of reactivatable
apoenzyme during chronic deficiency in vivo (7, 8), altered binding of
apoenzyme and coenzyme because of the presence of isoenzymes of transketolase (9), and reduced synthesis of
apoenzyme in patients with diabetes (10) and liver disease (11).
The cblE class may involve a reducing component of the MS system (84), whereas cblG is thought to be caused by defective MS
apoenzyme (85,86).
Biotin, pyridoxal-phosphate, and riboflavin can be covalently bound to the
apoenzymes and are called prosthetic groups.