酪氨酸265丙氨酸消旋酶作为基础抽象alpha-hydrogen丙氨酸:赖氨酸的同行残渣特定于D-alanine 39。
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三上渡边,Yoshimura T, B,江崎N
酪氨酸265丙氨酸消旋酶作为基础抽象alpha-hydrogen丙氨酸:赖氨酸的同行残渣特定于D-alanine 39。
,1999年10月,126 (4):781 - 6。
- PubMed ID
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10502689 (在PubMed]
- 文摘
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丙氨酸消旋酶的芽孢杆菌stearothermophilus提出了通过两个催化催化丙氨酸外消旋化基地:赖氨酸39 (K39)抽象具体D-alanine alpha-hydrogen和酪氨酸265 (Y265)扮演相应的角色对映体丙氨酸。K39的角色表示已经验证(渡边。黑川纪章,Y。Yoshimura, T。栗原市,T。苏打水,K。江崎,n(1999)生物。化学,274,4189 - 4194]。我们这里现在运作的证据Y265特定于丙氨酸为基础的催化剂。Y265——> Ala突变体酶(Y265A),如Y265S和Y265F,是个穷丙氨酸外消旋化的催化剂。然而,Y265A Y265S催化转氨作用与D-alanine更快比野生型酶和辅酶,吡哆醛5 '磷酸(PLP)被转换为吡哆胺5 '磷酸(PMP)。转氨作用催化率由野生型Y265F是大约9%的酶。beplayapp然而,Y265A Y265S, Y265F相似,丙氨酸在转氨作用是惰性基质。 The apo-form of the wild-type enzyme catalyzes the abstraction of tritium non-specifically from both (4'S)- and (4'R)-[4'-(3)H]PMP in the presence of pyruvate. In contrast, apo-Y265A abstracts tritium virtually from only the R-isomer. This indicates that the side-chain of Y265 abstracts the alpha-hydrogen of L-alanine and transfers it supra-facially to the pro-S position at C-4' of PMP. Y265 is the counterpart residue to K39 that transfers the alpha-hydrogen of D-alanine to the pro-R position of PMP.