Cancer cells commonly exhibit increased non-oxidative D-glucose metabolism whereas induction of mitochondrial metabolism may impair malignant growth. We have first used an in silico method named elementary mode analysis to identify inhibition of ALAT (L-alanine aminotransferase) as a putative target to promote mitochondrial metabolism. We then experimentally show that two competitive inhibitors of ALAT, L-cycloserine and ?-chloro-L-alanine, inhibit L-alanine production and impair D-glucose uptake of LLC1 Lewis lung carcinoma cells. The latter inhibition is linked to an initial energy deficit, as quantified by decreased ATP content, which is then followed by an activation of AMPK (AMP-activated protein kinase) and subsequently increased respiration rates and mitochondrial production of reactive oxygen species (ROS), culminating in ATP replenishment in ALAT-inhibited LLC1 cells. Moreover, we observe altered phosphorylation of p38 MAPK (mitogen-activated protein kinase 14), ERK (mitogen-activated protein kinase 1/2) and Rb1 (retinoblastoma 1) proteins, as well as decreased expression of Cdc25a (cell decision cycle 25 homolog A) and Cdk4 (cyclin-dependent kinase 4). Importantly, these sequelae of ALAT inhibition culminate in similarly reduced anchorage-dependent and anchorage-independent growth rates of LLC1 cells, altogether suggesting that inhibition of ALAT efficiently impairs cancer growth by counteracting the Warburg effect due to compensatory activation of mitochondrial metabolism.