Tylenda C A, Charon D, Lombardi F P, Gabriel O
Infect Immun. 1979 Feb;23(2):312-9. doi: 10.1128/iai.23.2.312-319.1979.
A careful examination of two strains of Actinomyces viscosus, T14V (virulent) and T14AV (avirulent), revealed no qualitative or quantitative difference in 6-deoxyhexose content of their cell surface. For a further study of the role of these sugars in cell surface-related phenomena, the stereochemical configuration of deoxyhexoses of A. viscosus T14 was established by two complementary approaches. (i) Examination of the biosynthetic pathway was found to lead to the formation of both 6-deoxy-l-talose and 6-deoxy-l-mannose and showed no differences in the ability of either bacterial strain, A. viscosus T14V or T14AV, to produce the precursors of these cell wall components. The biosynthetic pathway for 6-deoxy-l-talose and 6-deoxy-l-mannose was found to originate from deoxy-thymidine diphosphate (dTDP)-d-glucose, which in turn is converted to dTDP-4-keto-6-deoxy-d-glucose. Epimerization at carbons 3 and 5 of the hexose moiety of dTDP-4-keto-6-deoxy-d-glucose is followed by stereospecific reduction with reduced nicotinamide adenine dinucleotide phosphate to yield dTDP-6-deoxy-l-talose and dTDP-6-deoxy-l-mannose. In cell-free extracts of both A. viscosus T14 and T14AV, an identical ratio of 6-deoxy-l-talose to 6-deoxy-l-mannose of 1:8 was produced. Known precursors for the d-isomers of the same 6-deoxyhexoses such as guanosine diphosphate-d-mannose and dTDP-d-mannose were not converted by A. viscosus T14 cell-free extracts. (ii) Isolation of 6-[U-(14)C]deoxytalose and 6-[U-(14)C]deoxymannose from both strains of A. viscosus T14 was carried out by growing cells in a medium containing d-[U-(14)C]glucose. Again no qualitative or quantitative difference was noticeable between the two strains when 6-deoxy-hexoses were released from whole cells or purified cell walls by acid hydrolysis. Radioactive 6-[U-(14)C]deoxytalose isolated from the cell surface was used in an isotope dilution experiment to establish the stereochemical configuration of this 6-deoxyhexose. The radioactive sugar was mixed with unlabeled standard d- or l-6-deoxyhexose, respectively, and conversion to the corresponding 1-phenylflavazole derivative was carried out. Recrystallization to constant specific activity identified the radioactive sugar isolated from A. viscosus to be the l-isomer. A facile synthesis of the rare sugars 6-deoxy-l-talose and 6-deoxy-d-talose is reported.
对粘性放线菌的两株菌株T14V（有毒力）和T14AV（无毒力）进行仔细检查后发现，它们细胞表面的6 - 脱氧己糖含量在质和量上均无差异。为了进一步研究这些糖类在细胞表面相关现象中的作用，通过两种互补方法确定了粘性放线菌T14脱氧己糖的立体化学构型。（i）对生物合成途径的研究发现，该途径会导致6 - 脱氧 - l - 塔罗糖和6 - 脱氧 - l - 甘露糖的形成，并且在粘性放线菌T14V或T14AV这两种细菌菌株产生这些细胞壁成分前体的能力方面未发现差异。发现6 - 脱氧 - l - 塔罗糖和6 - 脱氧 - l - 甘露糖的生物合成途径源自脱氧胸苷二磷酸（dTDP）-d - 葡萄糖，其进而转化为dTDP - 4 - 酮 - 6 - 脱氧 - d - 葡萄糖。dTDP - 4 - 酮 - 6 - 脱氧 - d - 葡萄糖己糖部分的3号和5号碳原子发生差向异构化，随后用还原型烟酰胺腺嘌呤二核苷酸磷酸进行立体特异性还原，生成dTDP - 6 - 脱氧 - l - 塔罗糖和dTDP - 6 - 脱氧 - l - 甘露糖。在粘性放线菌T14和T14AV的无细胞提取物中，产生的6 - 脱氧 - l - 塔罗糖与6 - 脱氧 - l - 甘露糖的比例相同，均为1:8。粘性放线菌T14的无细胞提取物不会将已知的相同6 - 脱氧己糖d - 异构体的前体，如鸟苷二磷酸 - d - 甘露糖和dTDP - d - 甘露糖进行转化。（ii）通过在含有d - [U - (14)C]葡萄糖的培养基中培养细胞，从粘性放线菌T14的两株菌株中分离出6 - [U - (14)C]脱氧塔罗糖和6 - [U - (14)C]脱氧甘露糖。当通过酸水解从全细胞或纯化的细胞壁中释放6 - 脱氧己糖时，两株菌株之间同样未观察到质或量的差异。从细胞表面分离出的放射性6 - [U - (14)C]脱氧塔罗糖用于同位素稀释实验，以确定这种6 - 脱氧己糖的立体化学构型。将放射性糖分别与未标记的标准d - 或l - 6 - 脱氧己糖混合，并转化为相应的1 - 苯基黄酮唑衍生物。通过重结晶至恒定比活度确定从粘性放线菌中分离出的放射性糖为l - 异构体。本文报道了稀有糖类6 - 脱氧 - l - 塔罗糖和6 - 脱氧 - d - 塔罗糖的简便合成方法。
