In the field of metabolic engineering, phototrophic organisms are becoming more relevant due to increasing demands for sustainable solutions. An area within this field is the stringent response, a stress response pathway that involves the alarmones guanosine tetra- and pentaphosphate, collectively denoted (p)ppGpp. In this project, proteins that have previously been identified as potential regulatory targets of ppGpp in the plant Arabidopsis thaliana chloroplast and in cyanobacterium Synechocystis sp. PCC 6803 are purified and characterized. In Synechocystis, glucose-1-phosphate adenylyltransferase (glgC) and alpha-1,4 glucan phosphorylase (glgP2) involved in the glycogen metabolism were studied. In A. thaliana, lipoxygenase 2 (LOX2) in oxylipin metabolism and aspartate carbamoyltransferase (PyrB) in pyrimidine synthesis were studied. All proteins were successfully cloned into E. coli using gene fragments inserted into pET-28a(+) plasmids via Gibson assembly and purified using Immobilised Metal Affinity Chromatography (IMAC). Thermostability analysis in the presence and absence of ppGpp was conducted for glgC, LOX2, and PyrB with nano Differential Scanning Fluorimetry (nanoDSF). Because of insufficient yield, glgP2 was not subjected to nanoDSF analysis. For glgC and LOX2 results were inconclusive. Analysis of PyrB found clear indications of interaction with ppGpp for concentrations between 25 μM and 100 μM, as a dose-dependent shift of the melting curve toward a lower T_m was observed. Specificity of the binding was evaluated by also studying guanosine diphosphate (GDP) in place of ppGpp, which indicated interactions with PyrB at high concentrations (500 μM GDP). For PyrB, the regulation from ppGpp was further studied in an enzyme assay, which found a reduction of V_Max in the presence of ppGpp. In summary, these results may guide future research into the stringent response. This can have applications in metabolic engineering of phototrophic organisms, which will help meet the demand for sustainable solutions.