Complex sentence: They are decarboxylation of pyruvate (substrate 1) followed by reductive acetylation of lipoic acid (substrate 2), which is covalently bound to dihydrolipoamide acetyltransferase (E2), the second catalytic component enzyme of PDC.
Split into simpler sentences: They are decarboxylation of pyruvate (substrate 1) followed by reductive acetylation of lipoic acid (substrate 2). Lipoic acid is covalently bound to dihydrolipoamide acetyltransferase (E2), the second catalytic component enzyme of PDC.