Hydrolysis of Methylprednisolone Acetate by Human Serum Cholinesterase

The glucocorticoid and anti-inflammatory agent, methylpred-nisolone acetate (MpA), ’ is hydrolyzed to its active form, meth-ylprednisolone (Mp), in human whole blood (1). This report identifies human serum cholinesterase (EC3.l.l.8; acylcholine acylhydrolase: also called pseudocholinesterase, nonspecific cho-linesterase, butyrylcholinesterase) as one of the enzymes involved in this hydrolysis. Highly purified cholinesterase (2) appeared to be homogeneous on non-SDS gels and on SDS gels (3). The preparation was at least 99 % pure though a 1 % contaminant would have escaped detection. The specific activity of the purified cholinesterase was 198 imol. minmg when tested with benzoylcholine (50 iM benzoylcholine in 0.067 M sodium-potassium phosphate buffer, pH 7.4, 25#{176}C)(4) and 704 zmol.min’mg ’ when tested with butyrylthiocholine ( 1.0 mM butyrylthiocholine in 0. 1 M sodiu