Lee Won-Jae, Banavara Dattatreya S, Hughes Joanne E, Christiansen Jason K, Steele James L, Broadbent Jeffery R, Rankin Scott A
Division of Animal Science and Technology, Gyeongsang National University, Jinju, South Korea.
Appl Environ Microbiol. 2007 May;73(9):3034-9. doi: 10.1128/AEM.02290-06. Epub 2007 Mar 2.
Catabolism of sulfur-containing amino acids plays an important role in the development of cheese flavor. During ripening, cystathionine beta-lyase (CBL) is believed to contribute to the formation of volatile sulfur compounds (VSCs) such as methanethiol and dimethyl disulfide. However, the role of CBL in the generation of VSCs from the catabolism of specific sulfur-containing amino acids is not well characterized. The objective of this study was to investigate the role of CBL in VSC formation by Lactobacillus helveticus CNRZ 32 using genetic variants of L. helveticus CNRZ 32 including the CBL-null mutant, complementation of the CBL-null mutant, and the CBL overexpression mutant. The formation of VSCs from methionine, cystathionine, and cysteine was determined in a model system using gas chromatography-mass spectrometry with solid-phase microextraction. With methionine as a substrate, CBL overexpression resulted in higher VSC production than that of wild-type L. helveticus CNRZ 32 or the CBL-null mutant. However, there were no differences in VSC production between the wild type and the CBL-null mutant. With cystathionine, methanethiol production was detected from the CBL overexpression variant and complementation of the CBL-null mutant, implying that CBL may be involved in the conversion of cystathionine to methanethiol. With cysteine, no differences in VSC formation were observed between the wild type and genetic variants, indicating that CBL does not contribute to the conversion of cysteine.
含硫氨基酸的分解代谢在奶酪风味的形成中起着重要作用。在成熟过程中，胱硫醚β-裂解酶（CBL）被认为有助于挥发性硫化合物（VSC）如甲硫醇和二甲基二硫的形成。然而，CBL在特定含硫氨基酸分解代谢产生VSC中的作用尚未得到充分表征。本研究的目的是利用瑞士乳杆菌CNRZ 32的遗传变体，包括CBL缺失突变体、CBL缺失突变体的互补体和CBL过表达突变体，研究瑞士乳杆菌CNRZ 32中CBL在VSC形成中的作用。在一个模型系统中，使用带有固相微萃取的气相色谱-质谱法测定了甲硫氨酸、胱硫醚和半胱氨酸产生VSC的情况。以甲硫氨酸为底物时，CBL过表达导致VSC的产量高于野生型瑞士乳杆菌CNRZ 32或CBL缺失突变体。然而，野生型和CBL缺失突变体之间的VSC产量没有差异。以胱硫醚为底物时，在CBL过表达变体和CBL缺失突变体的互补体中检测到了甲硫醇的产生，这意味着CBL可能参与了胱硫醚向甲硫醇的转化。以半胱氨酸为底物时，野生型和遗传变体之间在VSC形成方面没有观察到差异，表明CBL对半胱氨酸的转化没有作用。
