The requirement for a low Km (at least micromolar) of this unusual enzymatic cancer drug stems from the fact that the intravenous l-asparaginase must be able to clear the circulating pools of l-Asn, which are not very high (about 50 μM) (Ollenschläger et al., 1988 ▸; Beckett & Gervais, 2019 ▸). The gene discussed is ASPG; the disease is cancer.