Figure 6

Orphan and non-orphan EC number distribution across superkingdoms. The green pie chart represents the proportion of orphan EC activities among all valid entries. Other pie charts represent the proportion of orphan activities among each superkingdom. An activity is considered as present in a superkingdom if at least one protein is annotated with corresponding EC number or the activity has been observed in an organism according to BRENDA database. The number and percentage of local and global orphans are given for each superkingdom. The small amount of characterized EC numbers in Archaea shows the obvious lack of knowledge about their metabolism.