Cholinesterases isoenzymes: a comparative study in the skin and plasma

Acetylcholinesterase (Ache) and pseudocholinesterase (BUche) activities were studied quantitatively in healthy skin by spectrophotometric methods and qualitatively by polyacrylamide gel electrophoresis. The results were compared to those obtained in plasma. The substrates used to reveal enzyme activities were acetylthiocholine (ATC) iodide and butyrylthiocholine (BTC) iodide, respectively. A linear relationship exists between the values of BUche and Ache activities in plasma and those in skin. Six isoenzymes of different electrophoretic mobility were observed in the skin. One of them, which is never found in plasma extracts, appears to be specific to the skin. On gradient gel electrophoresis, with both substrates (ATC and BTC), a single band of enzyme activity, corresponding to a molecular weight of 600,000 was observed. These results suggest that in the skin there is only one enzyme, most probably butyryl cholinesterase, which cleaves BTC somewhat faster than ATC. This methodology, when applied to the study of dermatoses in which abnormalities of cutaneous nerve terminals are suspected, should furnish precise functional pathophysiological details.