Phosphoserine phosphatase (PSP) catalyses the synthesis of l‐serine via the phosphorylated pathway by facilitating the dephosphorylation of phosphoserine. A cDNA encoding PSP from the silkworm Bombyx mori (bmPSP) was isolated using reverse transcription‐PCR and then sequenced. The resulting clone encoded 236 amino acids with a molecular weight of 26 150, exhibiting 14–60% sequence identity with other PSPs. The recombinant PSP was overexpressed in Escherichia coli and purified. Kinetic studies showed that bmPSP possessed activity toward l‐phosphoserine, and Asp20, Asp22 and Asp204 in bmPSP were found to be critical for modulating bmPSP activity. Real‐time PCR analysis provided evidence that the amount of bmpsp transcript was reduced in middle silk glands of a sericin‐deficient silkworm strain. These findings revealed that bmPSP may play important roles in synthesizing one‐carbon donors of l‐serine, which is abundant in silk, as well as other cell metabolites in B. mori.

中文翻译：

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蚕（Bombyx mori）参与L-丝氨酸合成的磷酸丝氨酸磷酸酶的分子研究。

磷酸丝氨酸磷酸酶（PSP）通过促进磷酸丝氨酸的去磷酸化，通过磷酸化途径催化1-丝氨酸的合成。使用逆转录-PCR分离了家蚕（bmPSP）的编码PSP的cDNA ，然后进行测序。所得克隆编码了236个氨基酸，分子量为26 150，与其他PSP的序列同一性为14-60％。重组PSP在大肠杆菌中过表达并纯化。动力学研究表明，bmPSP对l-磷酸丝氨酸具有活性，并且发现bmPSP中的Asp20，Asp22和Asp204对调节bmPSP活性至关重要。实时PCR分析提供了bmpsp量的证据丝胶缺乏型蚕品系的中间丝腺中的转录减少。这些发现表明，bmPSP可能在合成丝氨酸中丰富的l-丝氨酸的一碳供体以及家蚕中的其他细胞代谢物中起重要作用。