Arylesterase (EC 3.1.1.2) activity in serum was specifically measured using thiophenyl acetate in a mechanized assay at 37 degrees C with 4-bromophenylboronic acid as inhibitor of cholinesterase and hexacyanoferrate-III as indicator. The systematic development of a routine method, apparent limitations of thiophenyl compounds as arylesterase substrates, some kinetic constants of the enzyme, analytical variables such as precision (within-run <2% and between-run <2.5% relative standard deviation) and a preliminary reference interval (19.5-52.4 kU/l) for adults are described.
