Role of AMP Deaminase in : Implications for Nitrogen Utilization and Lipid Biosynthesis.

Lipid accumulation in oleaginous organisms is initiated by AMP deaminase (AMPD) after nitrogen depletion because it mediates the concentration of intracellular adenosine monophosphate (AMP). However, the role of AMPD in lipogenesis in the oleaginous fungus is largely unknown. Therefore, we identified the genes ( and ) encoding AMPD and investigated the role of AMPD in lipid synthesis in this fungus by overexpressing and deleting genes. Deletion of and caused 21 and 28% increments in lipid contents under N-limited conditions, respectively. These increases were correlated with the activation of enzymes involved in lipogenesis and the alteration of energy balance. Unexpectedly, overexpression of genes affected nitrogen consumption in both N-limited and N-excess media, which resulted in an increase in cell growth and lipid accumulation compared with the control strain when nitrogen was available. Furthermore, the increased lipid accumulation in the -overexpressing mutants in N-excess media was accompanied by enhanced activities of lipid biosynthetic enzymes. These data suggested that nitrogen metabolism and energy metabolism are affected by AMPD, and overexpression of genes induced lipid accumulation under nitrogen-rich conditions by mimicking the nitrogen limitation response. This highlights an intriguing function of AMPD in .