氨基酸作为一种迟效碳源无法被微生物快速利用。L-丝氨酸脱水酶(L-serine dehydratase,L-SerDH)可以将L-丝氨酸一步催化为丙酮酸和氨进入中心碳代谢生成生物量,且此过程不需要消耗ATP和还原力。L-丝氨酸是甲酸利用途径(还原性甘氨酸途径)的关键中间体。因此,改善L-丝氨酸的利用可以为甲酸和丝氨酸作为碳源利用提供参考价值。该文对巴斯德毕赤酵母(Pichia pastoris)进行了丝氨酸耐受性实验,结果显示毕赤酵母可以耐受20 g/L丝氨酸。对内源L-丝氨酸脱水酶在毕赤酵母中的表达进行了优化。在甘氨酸营养型毕赤酵母内分别表达了8种异源L-丝氨酸脱水酶,结果表示大肠杆菌tdcG基因编码的L-SerDH对丝氨酸利用改善效果最好,终OD600提高至出发菌株的1.6倍。该研究验证了巴斯德毕赤酵母对L-丝氨酸的耐受性,并筛选得到了较优的L-丝氨酸脱水酶来源,为毕赤酵母的丝氨酸利用提供了更优的酶来源。
Amino acids cannot be rapidly utilized by microorganisms as a gradually metabolized carbon source.L-serine dehydratase (L-SerDH) catalyzes the one-step conversion of L-serine into pyruvate and ammonia, facilitating central carbon metabolism to generate biomass without the consumption of ATP and reducing power.L-serine is a key intermediate in the formate utilization pathway (reductive glycine pathway).Therefore, improving the utilization of L-serine can provide valuable insights into the utilization of formate and serine as carbon sources.This paper explored serine tolerance of Pichia pastoris.Results demonstrated that P.pastoris exhibited tolerance to 20 g/L of L-serine.Expression optimization of endogenous L-serine dehydratase was carried out in P.pastoris.Eight heterologous L-serine dehydratases were expressed separately in glycine auxotroph P.pastoris.The results indicated that L-SerDH encoded by the E.coli tdcG gene had the best effect on the improvement of serine utilization, with the final OD600 increased to 1.6-fold that of the original strain.This study represents the validation of L-serine tolerance in P.pastoris and screens a superior source of L-serine dehydratase.These findings offer valuable insights into enhancing enzyme sources for serine utilization in P.pastoris.
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