Maruyama K, Kitamura H
J Biochem. 1985 Sep;98(3):819-24. doi: 10.1093/oxfordjournals.jbchem.a135340.
Mechanisms of growth inhibition by propionate on the growth of Rhodopseudomonas sphaeroides were studied. Partially purified pyruvate dehydrogenase complex (PDC) from R. sphaeroides was inhibited by propionyl-CoA, one of the metabolic intermediates of propionate, while propionate itself did not inhibit the enzyme. This suggests that the inhibitor of the growth in vivo is not propionate but propionyl-CoA. The inhibition by propionyl-CoA was competitive with respect to coenzyme A concentration. The K1 value for propionyl-CoA was 0.84 mM. Addition of NaHCO3, which restored the growth of this bacterium in the presence of propionate, increased the rate of propionate incorporation by 1.7-fold and decreased the intracellular level of propionyl-CoA by half. These findings suggest that HCO3-ion lowers the level of propionyl-CoA by accelerating its carboxylation reaction, which is catalyzed by propionyl-CoA carboxylase. Effects of NaHCO3 and acetate on the growth restoration were also studied by the use of propionyl-CoA carboxylase-deficient mutants. NaHCO3 did not restore the growth of the mutants, indicating an essential role of propionyl-CoA carboxylase on the restoration of growth by NaHCO3 as suggested above. Addition of acetate restores the growth of the mutants in the presence of propionate. Acetate probably restores the growth by supplying acetyl-CoA.
研究了丙酸盐对球形红假单胞菌生长的抑制机制。从球形红假单胞菌中部分纯化的丙酮酸脱氢酶复合物（PDC）受到丙酸盐的代谢中间产物之一丙酰辅酶A的抑制，而丙酸盐本身并不抑制该酶。这表明体内生长的抑制剂不是丙酸盐而是丙酰辅酶A。丙酰辅酶A的抑制作用在辅酶A浓度方面具有竞争性。丙酰辅酶A的K1值为0.84 mM。添加NaHCO3可在丙酸盐存在的情况下恢复该细菌的生长，使丙酸盐掺入率提高1.7倍，并使细胞内丙酰辅酶A水平降低一半。这些发现表明，HCO3-离子通过加速丙酰辅酶A羧化酶催化的羧化反应来降低丙酰辅酶A的水平。还通过使用丙酰辅酶A羧化酶缺陷型突变体研究了NaHCO3和乙酸盐对生长恢复的影响。NaHCO3不能恢复突变体的生长，表明如上文所述，丙酰辅酶A羧化酶在NaHCO3恢复生长中起着至关重要的作用。添加乙酸盐可在丙酸盐存在的情况下恢复突变体的生长。乙酸盐可能通过提供乙酰辅酶A来恢复生长。
