S. cerevisiae possess two catalase isoforms, a peroxisomal/mitrochondrial cta1 and an atypical cytosolic Ctt1.
Hence, we next addressed the relative importance of each isoform in protecting cells against H2O2 challenge using the single catalase knockouts, ctt1 and cta1. Comparable catalase activity is induced in wild-type and cta1 YPH250 cells after H2O2 exposure but negligible catalase induction occurs in the ctt1 mutant strain. Similar results were observed for the catalase knockout in the BY4741 genetic background (data not shown).