Pekala P H, Perfetti T, Hartline R A
Biochim Biophys Acta. 1975 Jun 11;394(1):65-75. doi: 10.1016/0005-2736(75)90205-9.
Alcaligenes denitrificans, pre-incubated with D-alpha-aminoadipate and assayed for L-isomer uptake without removal of extracellular D-isomer, exhibits a reduced rate of uptake and a reduced level at which steady state is achieved. During D- or L-isomer uptake, intracellular alpha-aminoadipate is exclusively the L-configuration. These data are consistent with an intracellular, mediated reduction in L-isomer uptake as the physiological basis for preferential D-alpha-aminoadipate uptake by A. denitrificans growing on racemic alpha-aminoadipate. Translocated D-alpha-aminoadipate is rapidly metabolized to form an L-isomer pool which subsequently reduces the rate of L-isomer uptake and the level at which steady state occurs resulting in a preferred D-isomer uptake. Competitive inhibition of L-alpha-aminoadipate uptake by the D-isomer or a difference in the maximum rates of uptate uptake is an inducible process expressed only in the presence of that compound and while uptake of L-alpha-animoadipate is also inducible there is a low rate of constitutive uptake. While L-alpha-aminoadipate uptake occurs against a concentration gradient, uptake of the D-isomer is not against a gradient. D- and L-isomer uptake are active processes since both are inhibited by azide, cyanide and 2,4-dinitrophenol.
将反硝化产碱菌与D-α-氨基己二酸预孵育，并在不除去细胞外D-异构体的情况下测定L-异构体摄取，结果显示摄取速率降低，达到稳态的水平也降低。在摄取D-或L-异构体期间，细胞内α-氨基己二酸仅为L-构型。这些数据与细胞内介导的L-异构体摄取减少一致，这是在消旋α-氨基己二酸上生长的反硝化产碱菌优先摄取D-α-氨基己二酸的生理基础。转运的D-α-氨基己二酸迅速代谢形成L-异构体池，随后降低L-异构体摄取速率和达到稳态的水平，从而导致优先摄取D-异构体。D-异构体对L-α-氨基己二酸摄取的竞争性抑制或摄取最大速率的差异是一个仅在该化合物存在时才表达的诱导过程，虽然L-α-氨基己二酸的摄取也是可诱导的，但组成型摄取速率较低。虽然L-α-氨基己二酸的摄取是逆浓度梯度进行的，但D-异构体的摄取不是逆梯度进行的。D-和L-异构体摄取都是主动过程，因为两者都受到叠氮化物、氰化物和2,4-二硝基苯酚的抑制。
