Role of the FAD-dependent polyamine oxidase in the selective formation of N¹,N⁸-bis(γ- glutamyl)spermidine protein cross-links¹

Protein-bound γ-glutamylpolyamines have highlighted a new pathway in polyamine metabolism. Human foreskin keratinocytes offer a suitable model for this study. Indeed, they develop polymerized envelopes, as they differentiate, rich in ϵ-(γ-glutamyl)lysine and N¹,N⁸-bis(γ-glutamyl)spermidine cross-links. We have found that the selective oxidation of N¹-(γ-glutamyl)spermidine and N-(γ-glutamyl)spermine by FAD-dependent polyamine oxidase (PAO) may be one of the cellular mechanisms regulating the preferential formation of a sterically defined bis(γ-glutamyl)spermidine cross-link. The significance of this finding is unknown, but it suggests that the target of this PAO-modulation is to achieve the biochemical prerequisite for production of a normal epidermal stratum corneum.