lysyl

The univalent radical of lysine.

- l. hydroxylase an enzyme that acts on specific l. residues in certain proteins ( E.G., collagens) with α-ketoglutarate and O₂ to produce δ-hydroxylysyl residues, succinate, and CO₂; this enzyme, which requires Fe²⁺ and ascorbate, is deficient in Ehlers-Danlos syndrome type VI. SYN: l. 2-oxoglutarate dioxygenase.

- l. oxidase an enzyme, which requires Cu²⁺ and O₂, that oxidizes certain l. residues in collagen to allysyl residues and hydroxylysyl residues to hydroxyallysyl residues; this is a required step for the cross-linking (via aldol condensations and Amadori rearrangements) of collagen strands; a lower activity of this enzyme is associated with occipital horn syndrome.

- l. 2-oxoglutarate dioxygenase SYN: l. hydroxylase.

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ly·syl 'lī-səl n the amino acid radical or residue H₂N(CH₂)₄CH(NH₂)CO- of lysine abbr. Lys

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ly·syl (liґsəl) the acyl radical of lysine.