cholesta-5,7,24-trienol為動物細胞膽固醇生合成路徑眾多中間產物之一，在工業上可做為calcifediol合成之起始物質，進一步合成calcitriol。calcitriol為具活性之維生素D3，人體可經由皮膚中大量之7-dehydrocholesterol吸收陽光中紫外線B (UVB)，再經由肝臟、腎臟代謝而產生具有最大活性之維生素D3 (calcitriol)。以往認為維生素D僅有助於強健骨骼、避免骨質疏鬆，但愈來愈多的研究發現維生素D與許多慢性病及免疫疾病息息相關。維生素D於臨床研究中被證實不僅能降低心臟病、糖尿病、憂鬱症、失智症、慢性疼痛、癌症、氣喘的發生，並可使人體提高免疫力以對抗疾病的發生。對於無法獲得足夠日曬或攝入足夠維生素D的族群而言，適當的補充維生素D是非常重要的。
本實驗欲使用代謝工程方法大量生產cholesta-5,7,24-trienol；利用erg5-erg6雙突變酵母菌進行cholesta-5,7,24-trienol之生合成，但由於cholesta-5,7,24-trienol生合成途徑含一速率決定步驟之酵素- HMG-CoA reductase，因此本實驗轉殖入帶有HMG-CoA reductase催化位序列之質體以增加酵母菌HMG-CoA reductase之反應速率，期望有助於提高cholesta-5,7,24-trienol之生合成產量。
　　藉由cholesta-5,7,24-trienol定量結果證明本實驗所建立之基因重組酵母菌 (ATCC NO. 74090/YIp352-tHMG) 確實可提高cholesta-5,7,24-trienol之產量，其百分比乾重可達0.86%，產量明顯高於未轉殖之酵母菌，因此適合做為cholesta-5,7,24-trienol之工業生產菌株，期望可應用於維生素D產業，以提高國產維生素D於國際市場之競爭力。

　　Cholesta-5,7,24-trienol is a metabolic intermediate of cholesterol biosynthetic pathway in animal cell, which is the initial compound of calcifediol synthesis in industry, and supplying for calcitriol synthesis. Calcitriol is the vitamin D3 with the highest activity, human body can obtain calcitriol by 7-dehydrocholesterol in skin. During exposure to sunlight, 7-dehydrocholesterol in epidermal and dermal cells absorbs ultraviolet B (UVB), it was then metabolized by liver and kidney; finally, we got active calcitriol. In the past, vitamin D was considered to regulate in calcium absorption and metabolism in intestine, kidney and skeleton. It can prevent osteoporosis. In recent years, more and more studies found that vitamin D not only can decrease the incidence of heart disease, diabetes, depression, demen-tia, chronicpain, cancer and asthma, but increase the immunity against diseases. It is very important to intake amount of vitamin D for people without enough sunlight and vitamin D.
　　The purpose of this research is to produce a large quantity of cholesta-5,7,24-trienol by metabolic engineering. This research utilized erg5-erg6 double-mutant yeast, which can accumulate cholesta-5,7,24-trienol and transformed a plasmid which carrying the sequence of catalytic domain of HMG-CoA reductase to improve the activity of HMG-CoA reductase who are rate-limiting step of cholesta-5,7,24-trienol biosynthesis.
The quantitative result verifies that the production of cholesta-5,7,24-trienol has significant increase, showing that the percentage of dry weight reach 0.86%, which is higher than the non-transformed yeast. This result strongly suggested that the gene-modified yeast can be applied in domestic vitamin D industry, increasing competition in international marketing.

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