Once fatty acids have been imported into the mitochondrial matrix by the carnitine acyltransferases, the beta-oxidation spiral begins. Each turn of this spiral concludes with the repetitive removal of two carbon units from the fatty acyl chain. beta-oxidation of saturated fatty acids (fatty acids with even numbered carbon chains and no double bonds) involves four different enzymatic steps: oxidation, hydration, a second oxidation, and a concluding thiolysis step, resulting in the two-carbon acetyl-CoA and a newly CoA primed acyl-CoA for the next turn of the spiral.