Molecular Structure of the COQ2 Enzyme (IMAGE) University of Toronto Caption Alternative splicing flips the inner core (shown in pink) of the COQ2 enzyme from the A variant, required for oxygen-fueled metabolism, to the E variant, shown here and required for anaerobic metabolism that sustains a parasite's life inside host body where oxygen levels are low. Credit Margot Lautens Usage Restrictions credit author License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.