Role of GlnK in regulating nitrogen metabolism and L-arginine synthesis in Corynebacterium crenatum

Abstract:

[Objective] In this study, we analyzed the roles of PII signal transduction protein GlnK in nitrogen metabolism regulation and L-arginine biosynthesis in Corynebacterium crenatum. [Methods] The glnK overexpressed, glnK deletion and glnK knock-down strains were constructed. RT-qPCR and determination of enzyme activities were carried out to reveal the effects of GlnK on the expression levels and enzyme activities of nitrogen metabolism-related and L-arginine biosynthesis-related genes and enzymes. The changes of various parameters during the fermentation of recombinant strains were also investigated. [Results] Overexpression of GlnK protein had a significant effect on the absorption of NH₄⁺. The expression levels and enzyme activities of nitrogen metabolism-related and L-arginine biosynthesis-related genes and proteins have generally been up-regulated in Cc-glnK strain. Among them, genes encoding ammonium absorption-related enzymes, such as glnA, gltD and gdh, were significantly up-regulated with an average increase about 4.58 times. The L-arginine yield and productivity of Cc-glnK reached 49.53 g/L and 0.516 g/(L·h), respectively, at the end of fermentation. [Conclusion] Overexpression of GlnK could promote the absorption of NH₄⁺, increase the expression levels of genes and enzymes activities on the L-arginine biosynthesis pathway, ultimately increase the yield of L-arginine. It provided guidance for the subsequent exploration of the nitrogen regulation mechanism and metabolic modification of C. crenatum in the production of nitrogen-containing compounds.

Key words:L-arginine;C. crenatum;nitrogen metabolism;PII signal transduction protein GlnK