Juillard V, Guillot A, Le Bars D, Gripon J C
Unité de Recherches Laitières et Génétique Appliquée, Centre de Recherches de Jouy-en-Josas, France.
Appl Environ Microbiol. 1998 Apr;64(4):1230-6. doi: 10.1128/AEM.64.4.1230-1236.1998.
To study the substrate specificity of the oligopeptide transport system of Lactococcus lactis for its natural substrates, the growth of L. lactis MG1363 was studied in a chemically defined medium containing milk peptides or a tryptic digest of alpha s2-casein as the source of amino acids. Peptides were separated into acidic, neutral, and basic pools by solid-phase extraction or by cation-exchange liquid chromatogrpaphy. Their ability to sustain growth and the time course of their utilization demonstrated the preferential use of hydrophobic basic peptides with molecular masses ranging between 600 and 1,100 Da by L. lactis MG1363 and the inability to use large, acidic peptides. These peptide utilization preferences reflect the substrate specificity of the oligopeptide transport system of the strain, since no significant cell lysis was inferred. Considering the free amino acid content of milk and these findings on peptide utilization, it was demonstrated that the cessation of growth of L. lactis MG1363 in milk was due to deprivation of leucine and methionine.
为研究乳酸乳球菌寡肽转运系统对其天然底物的底物特异性，在含有乳肽或αs2-酪蛋白胰蛋白酶消化物作为氨基酸来源的化学限定培养基中研究了乳酸乳球菌MG1363的生长情况。通过固相萃取或阳离子交换液相色谱法将肽分离为酸性、中性和碱性组分。它们维持生长的能力及其利用的时间进程表明，乳酸乳球菌MG1363优先利用分子量在600至1100 Da之间的疏水碱性肽，且无法利用大的酸性肽。这些肽利用偏好反映了该菌株寡肽转运系统的底物特异性，因为未推断出明显的细胞裂解。考虑到牛奶中的游离氨基酸含量以及这些关于肽利用的发现，证明了乳酸乳球菌MG1363在牛奶中生长停止是由于亮氨酸和蛋氨酸的缺乏。
