Optimized T. maritima I-1-Pase expression and purification with a 12% SDS–PAGE gel stained with Coomassie brilliant blue. Lane a, crude extract; lane b, heat-treated supernatant; lane c, pooled fractions obtained from the Q-Sepharose fast flow column; lane d, I-1-Pase obtained from the Phenyl-Sepharose column; lane 3, molecular mass standards (66, 45, 36, 29, 24, 21.4, and 14 kDa).