there is disclosed the preparation and recovery of proteins , in particular of enzymes , by controlled proteolytic cleavage of pro - proteins , in particular pro - enzymes , in a single method step , wherein a pro - protein - containing solution is contacted with a protease and with a solid carrier which has a higher affinity to the protein than to the pro - protein or to the functionally inactive degradation products thereof , the pro - protein being proteolytically cleaved to said protein , and the protein being selectively separated by absorption on the solid carrier .