Unusual Aggregation Properties of Single Amino Acid L-Lysine Hydrochloride

Abstract

.The self-assembly of single amino acids is very important topic of\nresearch since there are plethora of diseases like phenylketonuria,\ntyrosinemia, hypertryptophanemia, hyperglycinemia, cystinuria and maple syrup\nurine disease to name a few which are caused by the accumulation or excess of\namino acids. These are in-born errors of metabolisms (IEM’s) which are caused\ndue to the deficiency of enzymes involved in catabolic pathways of these\nenzymes. Hence, it is very pertinent to understand the fate of these excess\namino acids in the body and their self-assembling behaviour at molecular level.\nFrom the previous literature reports it may be surmised that the single amino\nacids like Phenylalanine, Tyrosine, Tryptophan, Cysteine and Methionine assemble\nto amyloid like structures, and hence have important implications in the pathophysiology\nof IEM’s like phenylketonuria, tyrosinemia, hypertryptophanemia, cystinuria and\nhypermethioninemia respectively. In this manuscript we report the self-assembly\nof lysine hydrocholride to fiber like structures in deionized water. It could\nbe observed that lysine assemble to globular structures in fresh condition and\nthen gradually changes to fiber like morphologies by self-association over time\nafter 24 hours. These fibers gradually change to tubular morphologies after 3\nday followed by fractal irregular morphologies in 10 and 15 days respectively. Notably,\nlysine exists as positively charged amino acid at physiological pH and the\namine groups in lysine remain protonated. Hence, the self-assembling properties\nof lysine hydrochloride in deionized water is also pertinent and give insights\ninto the fate of this amino acid in body in case it remains unmetabolized.\nFurther, MTT assays were done to analyse the toxicities of these aggregates and\nthe assay suggest their cytotoxic nature on SHSY5Y neural cell lines. Hence, the\naggregation of lysine may be attributed to the pathological symptoms caused in\ndiseases like hyperlysinemia which is associated with the neurological problems\nlike seizures and short-term memory as observed in case of amyloid diseases\nlike Parkinson’s and Alzheimer’s to name a few.