Selenium is an essential micronutrient for mammals, birds, and some bacteria. 1) Various selenium amino acids occur in nature, and most are physiologically active. Several enzymes contain selenocysteine as an integral moiety in their polypeptide chains.2- 4) However, little attention has been paid to the metabolism and phys- iological roles of selenium amino acids. Recently, we purified S-alkylcysteine a,j3-lyase (EC 4.4.1.6) from Pseudomonas putida ICR3640 to ...