Abstract: 【Aim】 Pyridoxal-5′-phosphate (PLP) functions as a coenzyme in many cellular processes including the interconversion and catabolism of amino acids. Pyridoxal kinase (PLK) is a key enzyme related to VB₆ metabolism. This study aims to reveal the relationship of transcription regulation between the kinase of PLP and the apo-B6 enzymes. 【Methods】 Three siRNAs (siRNA1, siRNA2 and siRNA3) based on PLK gene sequence were designed and synthesized, and injected to the day-3 5th instar larvae of the silkworm, Bombyx mori. The expression levels of phosphoserine aminotransferase (SerB) and asparate aminotransferase (AST) genes were detected by real-time quantitative PCR, to explore their interference effects on PLK replication. 【Results】 The best interference efficiency was achieved at 48 h after injection. The interference efficiency of the three fragments from high to low was siRNA1, siRNA2 and siRNA3. The interference efficiency was different in different tissues, and that in the midgut was the highest with the relative expression level of the PLK gene decreased by 55%. The relative expression levels of SerB and AST genes were also decreased by 90% and 29%, respectively, after RNA interference of PLK gene. 【Conclusion】 This study successfully down-regulated the PLK gene in B. mori  larvae. The results further demonstrate that phosphoserine aminotransferase (SerB) and asparate aminotransferase (AST) genes are related to the pyridoxal kinase gene.

Key words: Bombyx mori, pyridoxal kinase, pyridoxal-5′-phosphate, siRNA, real-time quantitative PCR, aminotransferase