Tanaka K, Tolbert N E, Gohlke A F
Plant Physiol. 1966 Feb;41(2):307-12. doi: 10.1104/pp.41.2.307.
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 K(m) was 1 x 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. Only a very slow hydrolysis of phosphorylcholine by similar plant extracts was observed. This phosphatase activity was purified 200- or 300-fold and appeared to be caused by a nonspecific acid phosphatase. The activity of both the kinase and the phosphatase did not seem sufficient to account for the rapid equilibration of the large phosphorylcholine reservoir of plants with exogenous P(32)-labeled orthophosphate.
胆碱激酶存在于大麦、小麦、烟草、菠菜和南瓜植株的根和叶中。该激酶从菠菜叶中纯化了25倍。该酶的最适pH范围较宽，在7.5至10.0之间。酶活性需要Mg(++)，并且在Mg(++)存在下酶相对稳定。当Mg(++)与ATP的比例为1:1时，可获得最大酶活性。米氏常数（K(m)）为1×10(-4)m。叶中的激酶与油菜籽或酵母中的激酶相似，只是叶和种子中的酶不受能与巯基结合的化合物的抑制。相似的植物提取物对磷酸胆碱的水解非常缓慢。这种磷酸酶活性被纯化了200至300倍，似乎是由一种非特异性酸性磷酸酶引起的。激酶和磷酸酶的活性似乎都不足以解释植物中大量磷酸胆碱库与外源P(32)标记的正磷酸盐之间的快速平衡。
