In muscle cells, we have predominantly the misosign, but in liver cells we have predominantly that l isosine of pyruvate kinase. And although they carry out the same type of catalytic and regulatory process, they do have slightly different properties. And that's because they have slightly different amino acid sequences and slightly different structures. So we see that isozymes are proteins that carry out the same type of biochemical process, but have slightly different amino acid sequences and slightly different structures. And so because of that, they display slightly different properties. For instance, they might have different mechanics, constant values, they might have different turnover numbers and so forth.