alaninePronunciation: /ˈaləniːn/Definition of alanine noun [mass noun] Biochemistry an amino acid which is a constituent of most proteins. Chemical formula: CH3CH(NH2)COOH Origin: mid 19th century: coined in German as Alanin, from aldehyde + -an (for ease of pronunciation) + -ine4alanine in other Oxford dictionaries Definition of alanine in the US English dictionary