代谢
三羧酸循环不仅用于将葡萄糖完全氧化成二氧化碳和水,还为一些次级代谢物的生物合成提供中间体,包括类胡萝卜素毒素...第一步涉及癸酸与草酰乙酸的缩合,这一过程类似于柠檬酸的形成。随后的脱水、脱羧和氧化导致形成一个中间酐,该酐二聚化并在进一步氧化后形成类胡萝卜素毒素A。氧气功能在哪个阶段引入尚不清楚,特别是,这样一个假设将意味着α,β-不饱和γ-内酯的羧基来自乙酸盐的甲基碳。/类胡萝卜素毒素/
AS WELL AS SERVING TO COMPLETE THE OXIDATION OF GLUCOSE TO CO2 & WATER, THE TRICARBOXYLIC ACID CYCLE ALSO PROVIDES INTERMEDIATES FOR THE BIOSYNTHESIS OF SOME SECONDARY METABOLITES, INCL THE RUBRATOXINS... THE FIRST STEP INVOLVES CONDENSATION OF DECANOIC ACID WITH OXALOACETIC ACID IN A MANNER ANALOGOUS TO THE FORMATION OF CITRIC ACID. SUBSEQUENT DEHYDRATION, DECARBOXYLATION & OXIDATION LEAD TO AN INTERMEDIATE ANHYDRIDE WHICH DIMERIZES TO FORM, AFTER FURTHER OXIDATION, RUBRATOXIN A. AT WHAT STAGE THE OXYGEN FUNCTIONS ARE INTRODUCED IS NOT CLEAR, &, IN PARTICULAR, SUCH A HYPOTHESIS WOULD MEAN THAT THE CARBOXYL GROUP OF THE ALPHA,BETA-UNSATURATED GAMMA-LACTONE WOULD BE DERIVED FROM THE METHYL CARBON OF ACETATE. /RUBRATOXINS/
来源:Hazardous Substances Data Bank (HSDB)