\selectlanguage{english}
\addchap{Abstract}
\acresetall
The objective of this work was the heterologous expression and purification of the pyruvate, phosphate dikinase (PPDK) from \ac{F. trinervia} and to provide evidence for its functional folding by conducting an activity assay.

Codon-optimized \acs{DNA} was cloned in an expression vector derived from pET-16b. Cells  of the \ac{E. coli} strain BL21 (DE3) were subsequently transformed using this vector and used for the expression of the \ac{PPDK}. The expressed protein was purified using its His-tag for an affinity chromatography. Yields of up to \SI{118}{\milli\gram\per\liter} culture could be achieved in high purity.

The functional folding of the expressed \ac{PPDK} was tested measuring \acs{CD} spectra in combination with a coupled enzyme assay in which pyruvate, \acs{ATP} and inorganic phosphate react to phosphoenolpyruvate (PEP), \acs{AMP} and pyrophosphate. Using this assay, the kinetic parameters of the heterologous expressed \acs{PPDK} from \acs{F. trinervia} could be obtained: the \ce{K_m} were measured as \SI[seperr]{50(9)}{\micro\Molar} (\acs{ATP}) and \SI[seperr]{270(44)}{\micro\Molar} (pyruvate), the specific activity was \SI[seperr]{0,99(9)}{\Unit\per\milli\gram}.

As a result of a size exclusion chromatography it could be shown that certain fractions of the purified \acs{PPDK} were monodisperse and hence suitable for crystallization experiments.

In conclusion, the \ac{PPDK} from \ac{F. trinervia} could be successfully expressed and purified to a high degree. Furthermore the purified protein was active and hence folded natively.
\selectlanguage{ngerman}