Additional evidence for the pivotal role of extracellular cysteines in the APN molecule was obtained
In contrast , the transmembrane Cys24 appears to have no similar function .
Additional evidence for the pivotal role of extracellular cysteines in the APN molecule was obtained when substitution of any of these six cysteines caused complete loss of surface expression and enzymatic activity .
In contrast , the transmembrane Cys24 appears to have no similar function .