Primary hyperoxaluria type I due to a point mutation of T to C in the coding region of the serine:pyruvate aminotransferase gene.

cDNA clones for serine:pyruvate aminotransferase (SPT, alternative name: alanine:glyoxylate aminotransferase) were obtained from a cDNA library constructed from the liver of a primary hyperoxaluria type I (PH1) case in which the SPT activity was approximately one-hundredth that in control liver. Six clones were isolated from 100,000 transformants and all of them contained an approximately 1.5 kbp insert which included the whole coding region for human SPT. Nucleotide sequence analysis revealed a point mutation of T to C at position 634 (relative to the 5'-end of the cDNA) encoding a Ser to Pro substitution at residue 205. The T to C conversion created a new SmaI site, which enabled us to demonstrate that the point mutation had occurred in the patient's SPT gene. SmaI digestion of genomic DNA may be useful for the diagnostic gene analysis of this type of PH1.