Lagunas R, Pestaña D, Diez-Masa J C
Biochemistry. 1984 Feb 28;23(5):955-60. doi: 10.1021/bi00300a024.
The spontaneous formation of arsenic mononucleotides has been detected in mixtures of arsenate and inosine or adenosine or its deoxy analogues. These compounds have been separated by high-performance liquid chromatography and identified by their behavior in the presence of myokinase and adenylate deaminase. The nucleoside 5'-arsenates are formed preferentially to the 2'- and 3'-arsenate analogues. All arsenic nucleotides detected showed similar kinetic and equilibrium constants of formation: about 8 X 10(-4) M-1 S-1 and 2 X 10(-3) M-1, respectively. These values are several orders of magnitude greater than those of their phosphoric analogues. The adenosine 5'-arsenate was able to substitute for 5'AMP in the reaction of myokinase and adenylate deaminase. The substitutions of the 2'- or 3'-hydrogen for hydroxyl groups in the ribose moiety of this compound slightly affected its suitability as substrate for myokinase but had drastic effect in the case of adenylate deaminase. The half-life of the arsenic nucleotides, at pH 7.0 and 25 degrees C, ranged from 30 to 45 min. The lability of these compounds is increased during catalysis with myokinase. Results on the reaction mechanism of myokinase with adenosine 5'-arsenate indicate that the mixed-anhydride analogue to ADP, adenosine 5'-(arsenate phosphate), is not detected either because it is not formed in the reaction with this enzyme or because it is rapidly hydrolyzed.
在砷酸盐与肌苷、腺苷或其脱氧类似物的混合物中已检测到砷单核苷酸的自发形成。这些化合物已通过高效液相色谱法分离，并通过它们在肌激酶和腺苷酸脱氨酶存在下的行为进行鉴定。核苷5'-砷酸盐比2'-和3'-砷酸盐类似物更优先形成。检测到的所有砷核苷酸显示出相似的形成动力学和平衡常数：分别约为8×10⁻⁴M⁻¹s⁻¹和2×10⁻³M⁻¹。这些值比它们的磷酸类似物的值大几个数量级。腺苷5'-砷酸盐能够在肌激酶和腺苷酸脱氨酶的反应中替代5'-AMP。该化合物核糖部分中2'-或3'-氢被羟基取代对其作为肌激酶底物的适用性略有影响，但对腺苷酸脱氨酶的情况有显著影响。在pH 7.0和25℃下，砷核苷酸的半衰期为30至45分钟。在用肌激酶催化期间，这些化合物的不稳定性增加。关于肌激酶与腺苷5'-砷酸盐反应机制的结果表明，未检测到与ADP的混合酸酐类似物腺苷5'-(砷酸磷酸)，要么是因为它在与该酶的反应中未形成，要么是因为它迅速水解。
