Britz M L, Wilkinson R G
Can J Microbiol. 1982 Mar;28(3):291-300. doi: 10.1139/m82-043.
Freshly compared cell suspensions of clostridia (Clostridium bifermentans, C. botulinum proteolytic type A, C. difficile, C. sordellii, and C. sporogenes) and Peptostreptococcus anaerobius converted leucine to isovaleric (iV) and isocaproic (iC) acids in the absence of other amino acids. The optimal pH for conversion was between 8 and 9 at 37 degrees C. The stoichiometry of reaction was compatible with that expected for the Stickland reaction, as the ratio of iV to iC was 1:2, the amount of CO2 produced was equivalent to that of iV, and ammonium ion concentrations were equal to the total C5 and C6 acids formed. The presence of alanine and valine (proton donors in the Stickland reaction) in incubations effectively increased the concentration of iC at the expense of iV production, implying that leucine acted there primarily as a proton acceptor. Glycine and proline (proton acceptors) stimulated both iV and iC production from leucine, but increases in iV concentrations were proportionately greater than for iC so that leucine was primarily a proton donor in the presence of proton acceptors. Glucose stimulated the conversion of leucine to volatile fatty acids but favoured iC production. Production of iC from leucine was inhibited by surface active compounds (cetyltrimethylammonium bromide and desoxycholate) as well as arsenite and iodoacetate. The redox dyes methyl viologen and phenosafranine inhibited iC production more severely than iV production, as did the nitroimidazole antimicrobial agent, metronidazole.
新鲜制备的梭菌（双发酵梭菌、蛋白水解型A肉毒杆菌、艰难梭菌、索氏梭菌和生孢梭菌）和厌氧消化链球菌细胞悬液在无其他氨基酸存在的情况下，可将亮氨酸转化为异戊酸（iV）和异己酸（iC）。转化的最适pH在37℃时为8至9。反应的化学计量与史氏反应预期相符，因为iV与iC的比例为1:2，产生的二氧化碳量与iV相当，铵离子浓度等于形成的总C5和C6酸量。孵育液中存在丙氨酸和缬氨酸（史氏反应中的质子供体）有效地增加了iC的浓度，但以iV产生为代价，这意味着亮氨酸在那里主要作为质子受体起作用。甘氨酸和脯氨酸（质子受体）刺激亮氨酸产生iV和iC，但iV浓度的增加与iC相比成比例更大，因此在有质子受体存在时亮氨酸主要是质子供体。葡萄糖刺激亮氨酸向挥发性脂肪酸的转化，但有利于iC的产生。表面活性化合物（十六烷基三甲基溴化铵和脱氧胆酸盐）以及亚砷酸盐和碘乙酸盐抑制亮氨酸产生iC。氧化还原染料甲基紫精和番红对iC产生的抑制比对iV产生更严重，硝基咪唑抗菌剂甲硝唑也是如此。
