xanthine + 5-phospho-alpha-D-ribose 1-diphosphate => XMP + diphosphate
xanthine + 5-phospho-alpha-d-ribose 1-diphosphate => xmp + diphosphate
xanthine + 5-phospho-alpha-D-ribose 1-diphosphate => XMP + diphosphate
xanthine + 5-phospho-alpha-d-ribose 1-diphosphate => xmp + diphosphate