Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara, Japan.
Int J Food Microbiol. 2010 Mar 31;138(1-2):181-5. doi: 10.1016/j.ijfoodmicro.2010.01.001. Epub 2010 Jan 11.
During bread-making processes, yeast cells are exposed to multiple stresses. Air-drying stress is one of the most harmful stresses by generation of reactive oxygen species (ROS). Previously, we discovered that the novel N-acetyltransferase Mpr1/2 confers oxidative stress tolerance by reducing intracellular ROS level in Saccharomyces cerevisiae Sigma1278b strain. In this study, we revealed that Japanese industrial baker's yeast possesses one MPR gene. The nucleotide sequence of the MPR gene in industrial baker's yeast was identical to the MPR2 gene in Sigma1278b strain. Gene disruption analysis showed that the MPR2 gene in industrial baker's yeast is involved in air-drying stress tolerance by reducing the intracellular oxidation levels. We also found that expression of the Lys63Arg and Phe65Leu variants with enhanced enzymatic activity and stability, respectively, increased the fermentation ability of bread dough after exposure to air-drying stress compared with the wild-type Mpr1. In addition, our recent study showed that industrial baker's yeast cells accumulating proline exhibited enhanced freeze tolerance in bread dough. Proline accumulation also enhanced the fermentation ability after air-drying stress treatment in industrial baker's yeast. Hence, the antioxidant enzyme Mpr1/2 could be promising for breeding novel yeast strains that are tolerant to air-drying stress.
在面包制作过程中，酵母细胞会受到多种压力的影响。风干压力是通过产生活性氧（ROS）而产生的最有害的压力之一。以前，我们发现新型 N-乙酰转移酶 Mpr1/2 通过降低酿酒酵母 Sigma1278b 菌株的细胞内 ROS 水平来赋予其氧化应激耐受性。在这项研究中，我们揭示了日本工业面包酵母具有一个 MPR 基因。工业面包酵母 MPR 基因的核苷酸序列与 Sigma1278b 菌株中的 MPR2 基因相同。基因敲除分析表明，工业面包酵母中的 MPR2 基因通过降低细胞内氧化水平参与风干应激耐受性。我们还发现，表达具有增强的酶活性和稳定性的 Lys63Arg 和 Phe65Leu 变体分别比野生型 Mpr1 增加了暴露于风干应激后面包面团的发酵能力。此外，我们最近的研究表明，积累脯氨酸的工业面包酵母细胞在面包面团中表现出增强的抗冻能力。脯氨酸积累也增强了工业面包酵母风干应激处理后的发酵能力。因此，抗氧化酶 Mpr1/2 可能是培育耐受风干应激的新型酵母菌株的有前途的方法。
