Shikata H, Egi Y, Koyama S, Yamada K, Kawasaki T
Department of Biochemistry, Hiroshima University School of Medicine, Japan.
Biochem Int. 1989 May;18(5):943-9.
Adenylate kinase isozyme 1 (AK1) catalyzes thiamin triphosphate (TTP) formation from thiamin diphosphate (TDP) and ADP. The properties of the TTP-synthesizing activity of purified AK1 from porcine skeletal muscle were studied. The activity was found to require TDP, ADP, and Mg2+, and ATP was only 14.4% as active as ADP. Thiamin monophosphate (TMP) and thiamin were not utilized as substrates. ADP was specific as a phosphate donor; and CDP, UDP, and GDP supported TTP formation at rates less than 1% of that with ADP. Optimal pH and temperature for the TTP-synthesizing activity were 10.0 and 37 degrees C, respectively. The activity showed saturation kinetics for both substrates, and the Km values for TDP and ADP were calculated to be 0.83 mM and 43 microM, respectively. The enzyme catalyzed the reverse reaction (TTP + AMP----TDP + ADP) and stoichiometry between TTP and TDP was demonstrated in the forward and reverse reactions.
腺苷酸激酶同工酶1（AK1）催化由硫胺素二磷酸（TDP）和ADP生成硫胺素三磷酸（TTP）。对从猪骨骼肌中纯化得到的AK1的TTP合成活性特性进行了研究。发现该活性需要TDP、ADP和Mg2+，而ATP的活性仅为ADP的14.4%。硫胺素单磷酸（TMP）和硫胺素不作为底物。ADP作为磷酸供体具有特异性；而CDP、UDP和GDP支持TTP形成的速率不到ADP的1%。TTP合成活性的最适pH和温度分别为10.0和37℃。该活性对两种底物均表现出饱和动力学，TDP和ADP的Km值分别计算为0.83 mM和43 μM。该酶催化逆反应（TTP + AMP→TDP + ADP），并且在正向和逆向反应中都证明了TTP和TDP之间的化学计量关系。
