This application provides the first observation of methylmalonylation/malonylation in organic acidemias (OAs), such as methylmalonic acidemia (MMA) and propionic acidemia (PA), which results in modification of enzymes in key pathways dysregulated in OAs, including sirtuin 5 (SIRT5). Hyperacylation of SIRT5 prevents it from de-acylating CPS1 (including removing methymalonyllation), which prevents activation of CPS1 and likewise, inhibits a key component of the glycine cleavage system, GCSH. Based on these observations, provided herein is a mutant form of SIRT5 containing four mutated lysines that cannot accept acyl groups, methods of its use for treating OA patients, and kits.