D-3-phosphoglycerate dehydrogenase from the silkwormBombyx mori: Identification, functional characterization, and expression

摘要

D-3-phosphoglycerate dehydrogenase (PHGDH) is a key enzyme involved in the synthesis ofl-serine. Despite the high serine content in silk proteins and the crucial role of PHGDH in serine biosynthesis, PHGDH has not been described in silkworms to date. Here, we identified PHGDH in the silkwormBombyx moriand evaluated its biochemical properties. On the basis of the amino acid sequence and phylogenetic tree, this PHGDH has been categorized as a new type and designated as bmPHGDH. The recombinant bmPHGDH was overexpressed and purified to homogeneity. Kinetic studies revealed that PHGDH uses NADH as a coenzyme to reduce phosphohydroxypyruvate. High expression levels ofbmphgdhmessenger RNA (mRNA) were observed in the middle part of the silk gland and midgut in a standard strain of silkworm. Moreover, a sericin-deficient silkworm strain displayed reduced expression ofbmphgdhmRNA. These findings indicate that bmPHGDH might play a crucial role in the provision ofl-serine in the larva ofB. mori.