Choline acetyltransferase in bovine pineal gland.

Recent studies from our laboratories have shown that the bovine pineal gland contains a muscarinic cholinergic receptor with a Kd value of 0.423 +/- 0.010 nM and a Bmax value of 69.75 +/- 20.91 fmol/mg protein. In order to substantiate further the possible existence of a pineal cholinergic transmission, we have measured the activity of choline acetyltransferase and delineated its kinetic properties in the bovine pineal gland. This enzyme exhibited an activity of 0.0339 +/- 0.0042 nmol/mg protein/min. Furthermore, the bovine pineal choline acetyltransferase possessed a Km value of 124.86 +/- 24.06 microM and a Vmax value of 0.0598 +/- 0.0034 nmol/mg protein/min for acetyl CoA, and a Km value of 3.11 +/- 0.94 mM and a Vmax value of 0.0155 +/- 0.0016 nmol/mg protein/min for choline. The presence of muscarinic cholinergic receptors along with a specific choline acetyltransferase are supportive evidences that the bovine pineal gland may receive cholinergic innervation.