Relationship of atypical phenylketonuria and a new type of carbonyl reductase which related to synthesize BH4

四氢生物蝶呤在某些神经递质的生物合成中起着重要作用。采用DEAE-Sepharose FF柱层析技术，将家蚕柠檬突变体中合成四氢生物蝶素（BH4）和6- pyruvoyl-tetrahydropterin（PPH4）的酶分离为两个组分，分别命名为羰基还原酶I （CR I）和羰基还原酶II （CR II）。当CR I与CR II在反应混合物中混合时，在NADPH存在下，PPH4被还原为BH4。此外，我们研究了几种属于醛酮还原酶（AKR1）家族成员的人类羰基还原酶如何从PPH4形成BH4。在这些实验中，AKR1A1, AKR1B1, AKR1C1， AKR1C2和AKR1C4将PPH4转化为1'-氧-2'-羟丙基四氢蝶呤，而AKR1C3将PPH4转化为1'-羟基-2'-氧丙基四氢蝶呤，这两个反应都只发生在NADPH存在的情况下。在NADPH存在的情况下，这两种羰基还原酶都不能单独催化PPH4转化为BH4。

Tetrahydrobiopterin plays an important role in the biosynthesis of certain neurotransmitters. Using DEAE-Sepharose FF column chromatography, we separated the enzyme that synthesizes tetrahydrobiopterin(BH4) from 6- pyruvoyl-tetrahydropterin(PPH4), which is different from sepiapterin reductase, in the lemon mutant of the silkworm, Bombyx mori , into two fractions, which were named carbonyl reductase I ( CR I ) and carbonyl reductase II ( CR II ). When CR I was mixed with CR II in the reaction mixture, PPH4 was reduced to BH4 in the presence of NADPH.Furthermore, we examined the formation of BH4 from PPH4 by several human carbonyl reductases which belong to the aldo-keto reductase ( AKR1) family members. In these experiments, AKR1A1, AKR1B1, AKR1C1, AKR1C2, and AKR1C4 converted PPH4 to 1'-oxo-2'-hydroxypropyl-tetrahydropterin, while AKR1C3 converted PPH4 to 1'-hydroxy-2'-oxopropyl-tetrahydropterin, both reactions occurred only in the presence of NADPH. Neither of these carbonyl reductases alone was able to catalyze the conversion of PPH4 to BH4 in the presence of NADPH.