Ornithine Decarboxylase in Skin

Ornithine decarboxylase (ODC) was discovered in animal tissues in 1968 [1,2] and interest in its activity and regulation has led to a rapidly and still expanding literature on the enzyme. Several comprehensive reviews have already appeared [3–6]. This article emphasizes our current knowledge of ODC in mammalian skin. The involvement of ODC in tumor promotion will be discussed only briefly, since several recent monographs review this subject [7]. The extensive literature on ODC in tissue culture systems will be omitted for the sake of brevity.Ornithine decarboxylase is the first enzyme in the biosynthetic pathway for the polyamines, putrescine, spermidine and spermine (Fig. 1). Putrescine is the immediate product of ODC; and spermidine and spermine are synthesized from putrescine by the addition of aminopropyl groups generated by the enzyme S-adenosyl-L-methionine decarboxylase. The polyamines spermidine and spermine are polycationic molecules which interact strongly with nucleic acids. Polyamines stabilize the structure of both DNA and RNA and also participate in many enzymatic reactions involving nucleic acids, such as transfer RNA aminoacylation, protein synthesis and RNA transcription [4,5]. Intracellular levels of polyamines and their biosynthetic enzymes are generally found to correlate with growth, though a cause and effect relationship has not been proven. Since ODC is the rate-limiting enzyme for polyamine synthesis, its control has been of primary interest and importance in most studies