Molecular survey of the phosphoserine phosphatase involved in L‐serine synthesis by silkworms (Bombyx mori)

• Published in: Insect molecular biology 2020-02, Vol.29 (1), p.48-55
• Main Authors: Haque, M. R., Hirowatari, A., Saruta, F., Furuya, S., Yamamoto, K.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Amino acids; Animals; Bombyx - enzymology; Bombyx - genetics; Bombyx - metabolism; Bombyx mori; Chemical synthesis; Cloning, Molecular; Complementary DNA; Dephosphorylation; DNA, Complementary - genetics; E coli; Escherichia coli; Insect Proteins - biosynthesis; Insect Proteins - metabolism; L-Serine; Larva - metabolism; Metabolites; Molecular weight; Phosphatase; Phosphoric Monoester Hydrolases - chemistry; Phosphoric Monoester Hydrolases - genetics; Phosphoric Monoester Hydrolases - metabolism; phosphorylated pathway; Phosphoserine; Phosphoserine phosphatase; Reverse transcription; serine; Serine - biosynthesis; Silk; Silk gland; silkworm; Silkworms
• ISSN: 0962-1075; 1365-2583
• DOI: 10.1111/imb.12609

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. A cDNA encoding phosphoserine phosphatase from the silkworm Bombyx mori (bmPSP) was isolated. Kinetic studies showed that bmPSP possessed activity toward l‐phosphoserine. Asp20, Asp22 and Asp204 in bmPSP were found to be critical for modulating bmPSP activity.