L-Histidine (His) is an essential amino acid displaying a unique properties profile, involved in a number of biological activities, e.g. in pH buffering, in metal ion chelation, and in oxidative species scavenging, which confer it many physiological properties as antioxidant, anti-inflammatory, and in erythropoiesis and immune system regulation (1).
While there are several pathways of His degradation, most catabolism is directed to protein turnover and glutamate production and begins with histidase-dependent deamination. Also, the minor pathways of His as a precursor of histamine and His-rich proteins and peptides make it unique among other amino acids (1).
As a nutritionally essential amino acid, a deficiency of His has been shown to reduce protein levels in plasma, which in turn reduced the immunity defense (2). In contrast, dietary His supplementation has recently been reported for its role in the immune system homeostasis (3), and for many demonstrable potential benefits in various clinical conditions, including cognitive and neurological disorders, metabolic and inflammatory syndromes, and malignancies (1). Plasma His levels have even been shown as specific biomarkers for intestinal mucosal damage in calves (4). Interestingly, His supplementation was recently shown to increase chemotherapeutic sensitivity in pediatric leukemia-bearing mice, an effect mediated by an increase of histidine degradation flux (5), thus suggesting that His supplementation may improve the effectiveness of therapeutic treatments in cancer patients (6, 7).
As relevant to the above, His emerges as a key amino acid whose level measurements would be valuable in many pathophysiological conditions. We have thus developed and validated a novel ELISA kit (#IS-I-1300R) for His quantitation, characterized by a detection limit of 1.4µM in a 10μL sample volume.
Sensitive & easy-to-implement
Typical standard curve obtained with the His ELISA kit (#IS-I-1300R) where the optical density (OD) is inversely correlated to the His concentration within a range of 5.3 to 390µM.
Cross-validated with LC/MS
His was quantified in human EDTA plasma samples from 40 subjects using #IS-I-1300R ELISA kit and by LC/MS. Correlation between both methods gave a R-squared value above 0.99, thereby confirming the accuracy of the immunoassay.