The kinase responsible for the phosphorylation of
d
-ribulose was purified 45.5-fold from a strain of
Escherichia coli
K-12 capable of growth on
d
-arabinose with no separation of
d
-ribulo- or
l
-fuculokinase activities. Throughout the purification, the ratios of activities remained essentially constant. A nonadditive effect of combining both substrates in an assay mixture; identical
K
m
values for adenosine triphosphate with either
l
-fuculose or
d
-ribulose as substrate; and, the irreversible loss of activity on both substrates, after removal of magnesium ions from the enzyme preparation, suggest that the dual activity is due to the same enzyme. A fourfold greater affinity of the enzyme for
l
-fuculose than for
d
-ribulose, as well as a higher relative activity on
l
-fuculose, suggest that the natural substrate for this enzyme is
l
-fuculose. The product of the purified enzyme, with
d
-ribulose as substrate, was prepared. The ratio of total phosphorous to ribulose phosphate was 1.01:1, indicating that the product was ribulose monophosphate. The behavior of the kinase product in the cysteine-carbazole and orcinol reactions, as well as the results of periodate oxidation assays, provided evidence that it was not
d
-ribulose-5-phosphate. Reaction of this compound with a cell-free extract of
E. coli
possessing
l
-fuculose-l-phosphate aldolase activity resulted in the production of dihydroxyacetone phosphate and glycolaldehyde. The kinase product failed to reduce 2,3,5-triphenyltetrazolium and possessed a half-life of approximately 1.5 min in the presence of 1
n
HCl at 100 C. These properties suggested that the phosphate group was attached to carbon atom 1 of
d
-ribulose.
从能够在d-阿拉伯糖上生长的大肠杆菌K-12菌株中,分离了负责磷酸化d-核糖醇的激酶,其纯化程度为45.5倍。在纯化过程中,活性比例基本保持不变。在测定混合底物时,两种底物的Km值相同,且去除酶制剂中镁离子后,两种底物的活性都不可逆地丧失,表明双重活性是由同一酶引起的。酶对l-岩藻糖的亲和力比对d-核糖醇高4倍,并且在l-岩藻糖上的相对活性更高,这表明该酶的天然底物是l-岩藻糖。用d-核糖醇作为底物制备了纯化酶的产物,总磷与核糖醇磷酸的比值为1.01:1,表明产物是核糖醇一磷酸盐。该酶的产物在半胱氨酸-咔唑和奥卡酚反应中的行为,以及过碘酸盐氧化测定的结果,证明它不是d-核糖醇-5-磷酸盐。将该化合物与具有l-岩藻糖-l-磷酸醛缩酶活性的大肠杆菌无细胞提取物反应,产生二羟基丙酮磷酸盐和甘醛。该酶的产物无法还原2,3,5-三苯基四唑,并在1 N HCl存在下的半衰期约为1.5分钟。这些性质表明磷酸基附着在d-核糖醇的碳原子1上。