Abstract
1. A study has been made of the enzymic hydroxylation of biphenyl by liver microsomal preparations from 11 species of animals, by using a fluorescence method for the micro-estimation of the hydroxylation products, 2- and 4-hydroxybiphenyl. 2. Livers from all species examined produced 4-hydroxybiphenyl, but only those from mice, hamsters, cats, coypus and frogs produced 2-hydroxybiphenyl as well. 3. Adult rat and rabbit livers produced only the 4-isomer, but livers from the young of these species also produced the 2-isomer. 4. The properties and requirements of the 4-hydroxylating enzyme of rabbit liver were studied. 5. The results are discussed and it is suggested that the 2- and 4-hydroxylating enzymes are different.