Institute of Microbiology, CAS, Beijing, 100101, China.
College of Life Science and Technology, Inner Mongolia Normal University, Hohhot, Inner Mongolia, 010022, China.
Microb Biotechnol. 2022 May;15(5):1652-1665. doi: 10.1111/1751-7915.13998. Epub 2022 Jan 5.
N -acetyl-α-lysine was found as a new type of compatible solutes that acted as an organic cytoprotectant in the strain of Salinicoccus halodurans H3B36. A novel lysine N -acetyltransferase gene (shkat), encoding an enzyme that catalysed the acetylation of lysine exclusively at α position, was identified from this moderate halophilic strain and expressed in Escherichia coli. Sequence analysis indicated ShKAT contained a highly conserved pyrophosphate-binding loop (Arg-Gly-Asn-Gly-Asn-Gly), which was a signature of the GNAT superfamily. ShKAT exclusively recognized free amino acids as substrate, including lysine and other basic amino acids. The enzyme showed a wide range of optimal pH value and was tolerant to high-alkali and high-salinity conditions. As a new member of the GNAT superfamily, the ShKAT was the first enzyme recognized free lysine as substrate. We believe this work gives an expanded perspective of the GNAT superfamily, and reveals great potential of the shkat gene to be applied in genetic engineering for resisting extreme conditions.
N-乙酰-α-赖氨酸被发现是一种新型的相容溶质，在极端嗜盐菌 Salinicoccus halodurans H3B36 中作为一种有机细胞保护剂发挥作用。从该中度嗜盐菌中鉴定出一种新型赖氨酸 N-乙酰基转移酶基因（shkat），编码一种专门在α位催化赖氨酸乙酰化的酶，并在大肠杆菌中表达。序列分析表明，ShKAT 含有一个高度保守的焦磷酸结合环（Arg-Gly-Asn-Gly-Asn-Gly），这是 GNAT 超家族的特征。ShKAT 专门识别游离氨基酸作为底物，包括赖氨酸和其他碱性氨基酸。该酶表现出广泛的最适 pH 值范围，并能耐受高碱性和高盐度条件。作为 GNAT 超家族的新成员，ShKAT 是第一个被识别为游离赖氨酸作为底物的酶。我们相信这项工作拓宽了对 GNAT 超家族的认识，并揭示了 shkat 基因在遗传工程中应用于抵抗极端条件的巨大潜力。
