Histidine ammonia-lyase is a cytosolic enzyme catalyzing the first reaction in histidine catabolism, the nonoxidative deamination of L-histidine to trans-urocanic acid. Histidine ammonia-lyase defects cause histidinemia which is characterized by increased histidine and histamine and decreased urocanic acid in body fluids. Several transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Apr 2012]
Forensic Context
A study in humans developed a multiplex RT-PCR assay for definitive body fluid identification, demonstrating that the mRNA marker histatin 3 (HIS) is specific for saliva identification [Fleming & Harbison DOI:10.1016/j.fsigen.2009.10.006]. The assay showed specificity, with HIS detected only in its target fluid, and a sensitivity requiring a minimum of 5 µl of saliva or 0.3 ng of total RNA input for successful detection, also functioning effectively in mixed body fluid samples. A study in human body fluid stains demonstrated that the co-extraction method successfully isolated high-quality RNA and DNA from saliva, with the HAL mRNA and DNA detectable from the lowest tested volume of 1.6 µl for body fluid identification [Alvarez et al. DOI:10.1016/j.ab.2004.09.002].