Choline Kinase and Phosphorylcholine Phosphatase in Plants

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Abstract
Choline kinase was present in barley and wheat roots and leaves of barley, wheat, tobacco, spinach and squash plants. The kinase was purified 25-fold from spinach leaves. The enzyme had a broad pH optimum between 7.5 and 10.0. Mg++ was required for activity and in the presence of Mg++ the enzyme was relatively stable. Maximum enzyme activity was obtained when the Mg++: ATP ratio was 1:1. The Km was 1 × 10−4 m. The kinase from leaves was similar to that from rapeseed or from yeast, except that the leaf and seed enzymes were not inhibited by compounds which attach sulfhydryl groups.