Rodríguez-Bustamante Eduardo, Maldonado-Robledo Gabriela, Arreguín-Espinosa Roberto, Mendoza-Hernández Guillermo, Rodríguez-Sanoja Romina, Sánchez Sergio
Departamento de Biología Molecular y Biotecnología del Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, México, D.F., 04510, Mexico.
Appl Microbiol Biotechnol. 2009 Sep;84(3):499-510. doi: 10.1007/s00253-009-1996-6. Epub 2009 Apr 24.
Tobacco aroma compounds were generated via lutein cleavage by the combined action of a yeast and a bacterium identified as Trichosporon asahii and Paenibacillus amylolyticus, respectively. In this study, an inverse relationship between glucose concentration and the generation of three compounds, present in the tobacco aroma profile, was observed in mixed cultures. In order to identify the organism sensitive to the sugar effect, both were grown separately. The presence of glucose suppressed beta-ionone production by T. asahii grown with lutein. However, the biotransformation of the ionone into its reduced derivatives (7,8-dihydro-beta-ionone and 7,8-dihydro-beta-ionol) by P. amylolyticus was not affected by the sugar. This pointed to the cleavage of lutein, a step within the process necessary for the synthesis of beta-ionone, as the target of the glucose effect. In vitro studies with crude extracts and concentrated cell-free medium derived from T. asahii cultures showed that the carotenoid breakdown activity was located extracellularly and only detected in supernatants from yeast cells grown in the absence of the sugar. Rather than an inhibition or a mechanism affecting the enzyme secretion, the glucose effect on lutein degradation comprised another regulatory level. Further experiments showed that the enzyme responsible for lutein breakdown and susceptible to the sugar effect exhibited a high degree of identity to fungal peroxidases, studied as well, for their involvement in carotenoid cleavage.
烟草香气化合物是通过分别鉴定为浅黄假丝酵母和淀粉解类芽孢杆菌的酵母和细菌的联合作用，经由叶黄素裂解产生的。在本研究中，在混合培养物中观察到葡萄糖浓度与烟草香气谱中存在的三种化合物的生成之间呈负相关。为了确定对糖效应敏感的生物体，将两者分别培养。葡萄糖的存在抑制了与叶黄素一起生长的浅黄假丝酵母产生β-紫罗兰酮。然而，淀粉解类芽孢杆菌将紫罗兰酮生物转化为其还原衍生物（7,8-二氢-β-紫罗兰酮和7,8-二氢-β-紫罗兰醇）不受糖的影响。这表明叶黄素的裂解，即β-紫罗兰酮合成过程中必需的一步，是葡萄糖效应的作用靶点。对来自浅黄假丝酵母培养物的粗提物和浓缩无细胞培养基的体外研究表明，类胡萝卜素分解活性位于细胞外，且仅在无糖条件下生长的酵母细胞的上清液中检测到。葡萄糖对叶黄素降解的影响并非抑制作用或影响酶分泌的机制，而是包含另一个调控水平。进一步的实验表明，负责叶黄素分解且对糖效应敏感的酶与真菌过氧化物酶具有高度同源性，后者也因参与类胡萝卜素裂解而被研究。
