12,18-didecarboxysiroheme + 2 CO2 => siroheme + 2 H(+)
12,18-didecarboxysiroheme + 2 co2 => siroheme + 2 h(+)
12,18-didecarboxysiroheme + 2 CO2 => siroheme + 2 H(+)
12,18-didecarboxysiroheme + 2 co2 => siroheme + 2 h(+)