Instituto de Biotecnologia Aplicada à Agropecuária - BIOAGRO, Departamento de Microbiologia, Universidade Federal de Viçosa, Viçosa, 36570-000 Minas Gerais, Brazil.
Benef Microbes. 2011 Sep;2(3):209-20. doi: 10.3920/BM2011.0025.
A basic requirement for the prediction of the potential use of lactic acid bacteria (LAB) in the dairy industry is the identification of specific genes involved in flavour-forming pathways. The probiotic Lactobacillus delbrueckii UFV H2b20 was submitted to a genetic characterisation and phylogenetic analysis of genes involved in protein catabolism. Eight genes belonging to this system were identified, which possess a closely phylogenetic relationship to NCFM strains representative, as it was demonstrated for oppC and oppBII, encoding oligopeptide transport system components. PepC, PepN, and PepX might be essential for growth of LAB, probiotic or not, since the correspondent genes are always present, including in L. delbrueckii UFV H2b20 genome. For pepX gene, a probable link between carbohydrate catabolism and PepX expression may exists, where it is regulated by PepR1/CcpA-like, a common feature between Lactobacillus strains and also in L. delbrueckii UFV H2b20. The well conserved evolutionary history of the ilvE gene is evidence that the pathways leading to branched-chain amino acid degradation, such as isoleucine and valine, are similar among L. delbrueckii subsp. bulgaricus strains and L. delbrueckii UFV H2b20. Thus, the involvement of succinate in flavour formation can be attributed to IlvE activity. The presence of aminopeptidase G in L. delbrueckii UFV H2b20 genome, which is absent in several strains, might improve the proteolytic activity and effectiveness. The nucleotide sequence encoding PepG revealed that it is a cysteine endopeptidase, belonging to Peptidase C1 superfamily; sequence analysis showed 99% identity with L. delbrueckii subsp. bulgaricus ATCC 11842 pepG, whereas protein sequence analysis revealed 100% similarity with PepG from the same organism. The present study proposes a schematic model to explain how the proteolytic system of the probiotic L. delbrueckii UFV H2b20 works, based on the components identified so far.
用于预测乳酸菌（LAB）在乳制品行业中的潜在用途的一个基本要求是鉴定参与风味形成途径的特定基因。益生菌 Lactobacillus delbrueckii UFV H2b20 经历了基因特征分析和参与蛋白质分解代谢途径的基因的系统发育分析。鉴定出属于该系统的 8 个基因，它们与 NCFM 株系代表的基因具有密切的系统发育关系，正如 oppC 和 oppBII 编码寡肽转运系统成分所证明的那样。 PepC、PepN 和 PepX 可能对 LAB 的生长（无论是益生菌还是非益生菌）都是必不可少的，因为相应的基因总是存在，包括在 L. delbrueckii UFV H2b20 基因组中。对于 pepX 基因，碳水化合物分解代谢和 PepX 表达之间可能存在联系，它受到 PepR1/CcpA 样的调节，这是乳酸菌株的共同特征，也存在于 L. delbrueckii UFV H2b20 中。ilvE 基因的良好保守进化历史证明，导致支链氨基酸（如异亮氨酸和缬氨酸）降解的途径在 L. delbrueckii subsp. bulgaricus 菌株和 L. delbrueckii UFV H2b20 之间是相似的。因此，琥珀酸参与风味形成可以归因于 IlvE 活性。L. delbrueckii UFV H2b20 基因组中存在氨基肽酶 G，而在几个菌株中不存在，这可能会提高蛋白水解活性和效率。编码 PepG 的核苷酸序列表明它是一种半胱氨酸内肽酶，属于 Peptidase C1 超家族；序列分析显示与 L. delbrueckii subsp. bulgaricus ATCC 11842 pepG 具有 99%的同一性，而蛋白质序列分析显示与同一生物体的 PepG 具有 100%的相似性。本研究提出了一个示意模型，解释了基于迄今为止鉴定的成分，益生菌 L. delbrueckii UFV H2b20 的蛋白水解系统是如何工作的。
