Clans are the highest classification level of P450 genes.
In a phylogenetic analysis of 2920 arthropod P450 sequences (Dermauw et al., 2020), six clans are well supported: CYP2 (100/98/68), CYP3 (100/100/74), CYP4 (98/99.7/75), CYP16 (100/100/100), CYP20 (100/100/100) and the mitochondrial clan (100/100/91). Three more clans (see below) have a more limited distribution (and are not shown in the figure).
Here is a lookup table showing which arthropod CYP family belongs to which clan.
132 CYP families in clan 2, 509 in clan 3, 569 in clan 4 and 63 in the mito clan. (5 in clan 16, 4 in clan 20, 2 in clan 19 and 1 in clan 53). (as of 5 May 2024). David Nelson has named more families, but not all are publicly available.
Here is a table showing the distribution of arthropod CYP sequences by clan and CYPome size for 74 full CYPomes.
Clan by clan discussions
The four major clans represented in arthropods
Additional clans with more limited distribution in arthropods
Nelson (1998) has introduced the notion of phylogenetically related CYP families as “clans”, but the precise criteria for naming Nelson's “clans” have not been clearly defined. The proliferation of CYP families is now so great that the “clan” designation has become a useful heuristic guide. A clan is a deep-branching group of CYP families. This is shown **here** for arthropod clans.
Gotoh (1993) had earlier introduced a nomenclature of higher order than CYP families, The E (for eukaryotic type) and B (for bacterial type) “classes” and subclasses (I, II, III, etc.) that regroup CYP families on the basis of phylogeny. This nomenclature has not been followed or updated. Unfortunately, it may have seeded the confusing Interpro classification.
With four major and five minor clans, CYP clan diversity in arthropods is much lower than in plants (26 clans, including 14 algae-specific clans) (Hansen et al., 2021), fungi (at least 17 clans) or vertebrates (11 clans) (Nelson, 2018).
There is no arthropod-specific clan, as all clans have representatives in other organisms as well.