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Title 

High intracellular levels of uridinemonophosphate under nitrogen limited conditions enhance metabolic flux of curdlan synthesis in Agrobacterium species

Authors 

Mi Kyung KimIn Young LeeJung Hun KohY H RheeYoung Hoon Park

Publisher 

Wiley-Blackwell

Issue Date 

1999

Citation 

Biotechnology and Bioengineering, vol. 62, no. 3, pp. 317-323

Keywords 

nucleotidescurdlan synthesisnitrogen limitationAgrobacterium sp.

Abstract 

Changes of intracellular nucleotide levels and their stimulatory effects on curdlan synthesis in Agrobacterium species were investigated under different culture conditions. Under nitrogen-limited conditions where curdlan synthesis was stimulated, intracellular levels of UMP were as high as 87 and those of AMP were 78 nmol/mg of cellular protein, while those under nitrogen- sufficient conditions were lower than 45 nmol/mg-protein. The levels of other nucleotides such as UDP, UTP, UDP-glucose, ADP, ATP, and ADP-glucose were lower than 30 nmol/mg-protein under both nitrogen-limited and sufficient conditions. The time profiles of curdlan synthesis and cellular nucleotide levels showed that curdlan synthesis had a positive relationship with intracellular levels of UMP and AMP. After the ammonium concentration in the medium fell below 0.1 g/L, intracellular levels of UMP and AMP increased, followed by curdlan synthesis. However, no significant changes in the specific activities of UMP kinase, UDP kinase, and UDP-glucose pyrophosphorylase were observed during cultivation. In vitro enzyme reactions for the synthesis of UDP-glucose, which serve as a precursor for curdlan synthesis, demonstrated that the synthesis of UDP-glucose increased with the increase of UMP concentration. In contrast, AMP had no effect on UDP-glucose synthesis at all. Addition of UMP in the medium increased the curdlan synthesis, whereas curdlan synthesis was inhibited in the presence of AMP. From these results, we concluded that only the higher intracellular UMP levels caused by nitrogen limitation in the medium enhance the metabolic flux of curdlan synthesis by promoting cellular UDP-glucose synthesis. The changes of intracellular nucleotide levels and their stimulating effects on curdlan synthesis in Agrobacterium species were investigated under different culture conditions. Under N-limited conditions, the intracellular levels of UMP and AMP were as high as 87 nmol/mg and 78 nmol/mg of the cellular protein, respectively. However, those under N-sufficient conditions had lower than 45 nmol/mg-protein. The levels of other nucleotides such as UDP, UTP, UDP-glucose, ADP, ATP, and ADP-glucose were lower than 30 nmol/mg-protein under both N-limited and N-sufficient conditions. The time profiles of curdlan synthesis and cellular nucleotide levels showed that curdlan synthesis had a positive relationship with intracellular levels of UMP and AMP.

ISSN 

0006-3592

Appears in Collections

1. Journal Articles > Journal Articles

Registered Date

2017-04-19


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