Abstract：
A heterologous cDNA probe from Petunia hybrida was used to isolate flavanone-3 beta-hydroxylase-encoding cDNA clones from carnation (Dianthus caryophyllus), china aster (Callistephus chinensis) and stock (Matthiola incana). The deduced protein sequences together with the known sequences of the enzyme from P. hybrida, barley (Hordeum vulgare) and snapdragon (Antirrhinum majus) enabled the determination of a consensus sequence which revealed an overall 84% similarity (53% identity) of flavanone 3 beta-hydroxylases from the different sources. Alignment with the sequences of other known enzymes of the same class and to related non-heme iron-(II) enzymes demonstrated the strict genetic conservation of 14 amino acids, in particular, of three histidines and an aspartic acid. The conservation of the histidine motifs provides strong support for the possible conservation of structurally similar iron-binding sites in these enzymes. The putative role of histidines as chelators of ferrous ions in the active site of flavanone 3 beta-hydroxylases was corroborated by diethyl-pyrocarbonate modification of the partially purified recombinant Petunia enzyme.
摘要：
来自矮牵牛的异源cDNA探针用于从康乃馨（Dianthuscaryophyllus）中分离编码黄烷酮3β-羟化酶的cDNA克隆，中国紫苑（Callistephuschinensis）和股票（Matthiolaincana）。推导出的蛋白质序列以及来自P.hybrida的酶的已知序列，大麦（Hordeumvulgare）和金鱼草（Antirrrhinummajus）能够确定共有序列，该序列显示来自不同来源的黄烷酮3β-羟化酶的总体相似性为84％（53％同一性）。与相同类别的其他已知酶的序列和相关的非血红素铁-（II）酶的比对证明了14个氨基酸的严格遗传保守性，特别是,三个组氨酸和一个天冬氨酸.组氨酸基序的保守性为这些酶中结构相似的铁结合位点的可能保守性提供了强有力的支持。通过部分纯化的重组矮牵牛酶的二乙基-焦碳酸盐修饰，证实了组氨酸在黄烷酮3β-羟化酶活性位点中作为亚铁离子螯合剂的推定作用。
