Boyer T D, Zakim D, Vessey D A
Biochem Pharmacol. 1983 Jan 1;32(1):29-35. doi: 10.1016/0006-2952(83)90647-0.
The ability of the soluble glutathione S-transferases to bind the membrane (liposome) bound substrates 1-chloro-2,4-dinitrobenzene and sulfobromophthalein was determined. The transferases were found to have access only to substrates in the aqueous phase. They could not not bind membrane-bound substrates and, thus, enzymatic activities were reduced by the membrane partitioning of the substrates. The reduction in enzymatic activity was directly proportional to the lipid solubility of the substrate. The liposomes had no direct effect on the enzyme per se. [35S]Sulfobromophthalein and [14C]chlorodinitrobenzene bound to liposomes were found to have rapid rates of release into the aqueous phase. Rates of hydration of chlorodinitrobenzene from liposomes were rapid enough such that rates of catalysis (measured in a stopped-flow spectrophotometer) were affected only by the partition coefficient of substrate between lipid phase and water, and not by the rate of transfer of substrate from lipid to water phase.
测定了可溶性谷胱甘肽S-转移酶结合膜（脂质体）结合底物1-氯-2,4-二硝基苯和磺溴酞的能力。发现转移酶只能接触水相中的底物。它们不能结合膜结合的底物，因此，底物的膜分配会降低酶活性。酶活性的降低与底物的脂溶性成正比。脂质体本身对酶没有直接影响。发现结合到脂质体上的[35S]磺溴酞和[14C]氯二硝基苯迅速释放到水相中。氯二硝基苯从脂质体的水合速率足够快，以至于催化速率（在停流分光光度计中测量）仅受底物在脂质相和水之间的分配系数影响，而不受底物从脂质相转移到水相的速率影响。
