Some Characteristics of the Night N‐Acetyltransferase in the Rat Pineal Gland

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Abstract
Following lights on at night, the level of N-acetyltransferase declines, at first rapidly and then slowly after 20 min. The night N-acetyltransferase and the residual N-acetyltransferase 20 min after lights were on were characterized. Both enzymes had pH optimum 6.8 and were inactivated thermally in vitro with a half time of 8 min. Pre-treatment with cycloheximide or puromycin did not block the rise in N-acetyltransferase following isoproteneraol administration shortly after lights on. Night N-acetyltransferase apparently is 1 enzyme. After lights on, the enzyme rapidly deactivates to a less active form. Isoprotenerol applied within a short time may partly reactivate the enzyme.