Cloning and characterization of Arabidopsis thaliana pyridoxal kinase
Cloning and characterization of Arabidopsis thaliana pyridoxal kinase
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DOI：
10.1007/s00425-002-0799-0
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发表时间：
2002-06
期刊：
影响因子：
4.3
通讯作者：
H. Lum;F. Kwok;S. Lo
中科院分区：
文献类型：
--
作者：
H. Lum;F. Kwok;S. Lo
吡哆醛激酶（Pyridoxal kinase，PK; EC 2.7.1.35）是从拟南芥（Arabidopsis thaliana（L.）嘿和表征了A.发现thalianaPK与哺乳动物酶相似，同源性超过40%。表征研究表明，激酶是由两个相同的亚基组成的二聚体分子，每个亚基具有约35 kDa的分子量。该酶在pH 6.0时具有最大活性。类似于哺乳动物的酶，来自A的酶。Thalian用Zn ~（2+）代替常用的Mg ~（2+）作为催化剂的二价阳离子。在最适条件下，该酶的Vmax为604 nmol吡哆醛5′-磷酸（PLP）mg-1 min-1，对吡哆醛和ATP的Km值分别为688 μM和98 μM。酶表达水平的检查表明，叶，茎，根和花可以独立地产生PLP在相似的水平。此外，PK基因在A.在吸胀后60 h发现thalianaseeds开始。本研究的结果表明，植物组织依赖于PK生产PLP。
Pyridoxal kinase (PK; EC 2.7.1.35), a key enzyme in vitamin B6metabolism, was cloned fromArabidopsis thaliana(L.) Heynh. and characterized. The amino acid sequence of theA. thalianaPK was found to be similar to the mammalian enzyme, with a homology of more than 40%. Characterization studies showed that the kinase is a dimeric molecule consisting of two identical subunits, each subunit having a molecular mass of approximately 35 kDa. The enzyme exhibited maximal activity at pH 6.0. Similar to the mammalian enzyme, the enzyme fromA. thalianapreferred Zn2+instead of the commonly used Mg2+as the divalent cation for catalysis. Under optimal conditions, theVmaxof the enzyme was 604 nmol pyridoxal 5′-phosphate (PLP) mg–1min–1, and theKmvalues for pyridoxal and ATP were 688 µM and 98 µM, respectively. Examination of levels of enzyme expression showed that leaves, stems, roots and flowers can generate PLP independently at similar levels. Furthermore, expression of the PK gene inA. thalianaseeds was found to start 60 h after imbibition. Results from the present study suggest that plant tissues depend on PK for the production of PLP.