Characterization of choline O-acetyltransferase (ChAT) in the BALB/C mouse spleen

The synthesizing enzyme, Choline-O-acetyl transferase (ChAT) (EC 2.3.1.6) and the degradation enzyme, acetylcholinesterase (EC 3.1.1.7) for the neurotransmitter acetylcholine, have been anatomically and biochemically characterized in the thymus of the BALB/C mouse. In the present study we continue to analyze the possibility of cholinergic immunomodulation of immune tissues by determining if ChAT is present in the BALB/C mouse spleen. Our enzymatic evaluation of ChAT activity in splenic extracts revealed .05 nmoles/min/mg protein as compared to .1 nmoles/min/mg of protein activity in controls prepared from whole brain extracts. No detectable levels of ChAT activity were observed in the serum. Immunoblotting and immunoprecipitating using the anti ChAT monoclonal antibody, MB16, demonstrated two bands in the brain and one band in the spleen. Membrane bound ChAT in the brain was composed of two subunits with apparent molecular weights of 28 and 50 kDa. The spleen demonstrated only one form of ChAT with an apparent molecular weight of 28 kDa. Immunoprecipitation of the enzyme from both the brain and spleen resulted in a recovery of 59% and 60% of the activity respectively.