Catalases isoelectric point

Typically, all carefully characterized catalases are oligomers (isoelectric point 5.5) containing four (43-43) tetrahedrally arranged (47),... 

Typically, all carefully characterized catalases are oligomers (isoelectric point 5.5) containing four (43-46) tetrahedrally arranged (47), 60,000-dalton subunits (48-60). Each subunit consists of a single polypeptide chain (41) that associates with a single prosthetic group, ferric protoporphyrin IX (61). The subunits apparently function independently of one another (62, 63). 

In a schematic elution pattern of some standard proteins, peroxidase was eluted first with saline, BSA came next with glycine buffer at pH 6.6 and hemoglobin and catalase were eluted at a pH of nearly 8.0. Aldolase, lysozyme, chymotrypsinogen A, malate dehydrogenase, and cytochrome c were not eluted under these conditions, but were eluted with 0.1% SDS. The adsorption order does not depend on the isoelectric point, the molecular mass, or the content of basic amino acids. However, adsorption may depend on the o -helix content, and the secondary structure of those proteins may be important. We have also reported on protein adsorption and separation on siliconized glass surfaces (30), and on the adsorption and separation of nucleic acids on those same surfaces (31-35). 

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