A new sulfur amino acid, named hawkinsin, identified in a baby with transient tyrosinemia and her mother.

ABSTRACT

An unknown compound present in the urine of a girl with prolonged transient tyrosinemia and her mother was isolated and identified as (2-L-cystein-S-yl-1,4-dihydroxycyclohex-5-en-1-yl)-acetic acid (IVa). The new amino acid was named hawkinsin (Haw) and characterized by gas chromatography-mass spectrometry (GC-MS) of its penta-trimethylsilyl (TMS) derivative and of its desulfuration components. Haw was compared with the synthetic reference compound using GC-MS, IR, TLC, PC, ion-exchange chromatogrpahy and high-voltage electrophoresis. IVa and (2,6-bis-L-cystein-S-yl-1,4-dihydroxycyclohexyl-1)-acetic acid were synthesized from 4-quinolacetic acid, the latter was prepared in two different ways. It is postulated that Haw originates from an intermediate in the 4-hydroxy-phenylpuruvate hydroxylase reaction (EC 1.14.2.2), and that mother and child are heterozygous for an inborn error of metabolism characterized by a defect in this hydroxylase system, which is unable to rearrange the intermediate to homogentisic acid.