**2.20** γ**-Glutamylcysteine synthetase (Gcs, EC 6.3.2.2)**

Gcs is an essential protein of the trypanothione biosynthesis pathway, which catalyzes ATP-dependent ligation of L-cysteine to L-glutamate. Characterization of *L. donovani* Gcs was reported to the literature in 2016 [208]. Agnihotri et al. identified carbamate, urea, and purine derivatives as Gcs inhibitors using *in silico* tools, then antileishmanial effect of the compounds was reported *in vitro* [209].

#### **2.21 Cyclophilin (Cyp, Peptidylprolyl isomerase, EC 5.2.1.8)**

Cyclophilins are a ubiquitous class of proteins with peptidylprolyl *cis-trans* isomerase activity. The structure of cyclophilin from *L. donovani* bound to cyclosporin was reported in 2009 [210]. Interestingly, a recent study showed that cyclosporin A, cyclophilin A modulator, does not express any significant inhibitory effect on intracellular *L. donovani* amastigotes, therefore, further studies are needed to validate this enzyme [211].

### **2.22 Other** *Leishmania sp.* **enzymes**

We have summarized the validated targets for antileishmanial drug discovery and tried to give examples of potential modulators of these targets so far. Up to our knowledge, there are several other enzymes involved in kinetoplastids' physiological pathways which might serve as a potential target and provide selectivity, such as NDKb (nucleoside diphosphate kinase B, C 2.7.4.6), GPD (glycerol-3-phosphate dehydrogenase, EC 1.1.1.8), PGI (glucose-6-phosphate isomerase, EC 5.3.1.9), GspS (glutathionylspermidine synthetase, EC 6.3.1.8), PMM (phosphomannomutase, EC 5.4.2.8), PyK (pyruvate kinase, EC 2.7.1.40), TIM (triosephosphate isomerase, EC 5.3.1.1.), DHS (deoxyhypusine synthase, EC 2.5.1.46), and DOHH (deoxyhypusine hydroxylase, EC 1.14.99.29). Yet, the antileishmanial effect by the modulation of these targets has not been reported therefore further studies on these targets are needed.
