Wang Reuben, Lin Pei-Yin, Huang Shyue-Tsong, Chiu Chun-Hui, Lu Ting-Jang, Lo Yi-Chen
Institute of Food Science and Technology, National Taiwan University , No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan.
College of Bioresources and Agriculture, Joint Center for Instruments and Researches , No. 81, Changxing Street, Da-an District, Taipei 10617, Taiwan.
J Agric Food Chem. 2015 Dec 2;63(47):10271-9. doi: 10.1021/acs.jafc.5b03909. Epub 2015 Nov 19.
Bacteria and fungi can secrete extracellular enzymes to convert macromolecules into smaller units. Hyperproduction of extracellular enzymes is often associated with alterations in cell wall structure in fungi. Recently, we identified that Saccharomyces cerevisiae kre6Δ mutants can efficiently convert mogroside V into mogroside III E, which has antidiabetic properties. However, the underlying efficient bioconversion mechanism is unclear. In the present study, the mogroside (MG) bioconversion properties of several cell wall structure defective mutants were analyzed. We also compared the cell walls of these mutants by transmission electron microscopy, a zymolyase sensitivity test, and a mannoprotein release assay. We found zymolyase-sensitive mutants (including kre1Δ, las21Δ, gas1Δ, and kre6Δ), with defects in mannoprotein deposition, exhibit efficient MG conversion and excessive leakage of Exg1; such defects were not observed in wild-type cells, or mutants with abnormal levels of glucans in the cell wall. Thus, yeast mutants defective in mannoprotein deposition may be employed to convert glycosylated bioactive compounds.
细菌和真菌可以分泌胞外酶，将大分子转化为更小的单位。胞外酶的过量产生通常与真菌细胞壁结构的改变有关。最近，我们发现酿酒酵母kre6Δ突变体能够有效地将罗汉果甜苷V转化为具有抗糖尿病特性的罗汉果甜苷III E。然而，其潜在的高效生物转化机制尚不清楚。在本研究中，分析了几种细胞壁结构缺陷突变体的罗汉果甜苷（MG）生物转化特性。我们还通过透射电子显微镜、溶菌酶敏感性试验和甘露糖蛋白释放试验对这些突变体的细胞壁进行了比较。我们发现，溶菌酶敏感突变体（包括kre1Δ、las21Δ、gas1Δ和kre6Δ），其甘露糖蛋白沉积存在缺陷，表现出高效的MG转化和Exg1的过度泄漏；在野生型细胞或细胞壁中葡聚糖水平异常的突变体中未观察到此类缺陷。因此，甘露糖蛋白沉积有缺陷的酵母突变体可用于转化糖基化生物活性化合物。
