Moreover, knockdown of protein phosphatase Mg2 + /Mn2 + -dependent 1 K (PPM1K), the rate-limiting enzyme for the degradation of branched-chain amino acids (BCAAs), leads to massive accumulation of cytoplasmic BCAAs.60 PPM1K knockdown also significantly enhances E3 ubiquitin ligase CDC20-mediated downregulation of various proteins, thus causing impaired and dysfunctional metabolism and HSC quiescence.60 These mechanisms may play an important regulatory role in malignant transformation to leukemia. Here, PPM1K is linked to leukemia.