Recombinant L‐Asparaginase B and its Crystallization – What is the Nature of Protein Crystals?

L‐Asparaginase is a protein produced by Escherichia coli and exists in two types, A and B. Only type B shows a specific antitumor activity to acute lymphatic leukemia. A new recombinant E. coli BL21Gold (DE3) pET11a‐ansB was used to produce L‐asparaginase B in higher quantities. To enhance the purity and preserve the activity of L‐asparaginase B, crystallization is a promising process. Based on available patents, first experiments on L‐asparaginase B crystallization were performed. Recombinant L‐asparaginase B was successfully and reproducibly crystallized in two modifications. Up to now, it is not clear in which respect these two modifications of crystalline L‐asparaginase B differ. It is part of the current study to investigate the nature of protein crystals in detail. The investigations on lysozyme crystals are well in agreement with the literature.