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First, you have to create a matrix with all enzyme classes where each cell corresponds to an enzyme class. You can download the enzyme classes in the Enzyme Database: enter link description here

To compare two EC numbers, you have to convert the EC number to a bit array of the same size as the enzyme class matrix where each cell corresponds to the presence or absence of the enzyme class.

After that, apply jaccard similarity using two sets where it results in the degree of similarity between 0 (dissimilarity) and 1 (similar).