A second CYP26P450 in humans and zebrafish: CYP26B1

A new P450 gene has been found in humans. It has 44% sequence identity to C YP26A1 from human and mouse, which places it in a new subfamily, CYP26B. Th ere is only one human EST from a retinal library (AA012833) that matches th e coding region. Mo homologous ESTs are found in mouse. A zebrafish EST AI7 21901 shows 68% identity to the human protein. This zebrafish EST is only 4 1% identical to the zebrafish CYP26A1 protein sequence, so it represents th e homolog of the human CYP26B1 sequence. It is not known if this gene produ ct will act on all-trans-retinoic acid like the CYP26A1 protein or if it mi ght hydroxylate the 9-cis- or 13-cis-retinoic acid isoforms not recognized by CYP26A1. The importance of the CYP26A1 P450 in mouse and zebrafish devel opment flags the CYP26B1 gene as a potential developmental gene. (C) 1999 A cademic Press.