The gene for carnosinase is located on chromosome 18,[3] an autosome. The carnosine dipeptidase-1 gene (CNDP1) controls tissue and serum carnosinase.[10] Mutations in CNDP1 are responsible for carnosinase deficiency, resulting in carnosinemia.[3]
Carnosinemia is an autosomal recessive disorder,[3] which means the defective gene is located on an autosome, and two copies of the defective gene - one from each parent - are required to inherit the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.[citation needed]
1. Cellular, or tissue carnosinase:[12] This form of the enzyme is found in every bodily tissue. It is a dimer, and hydrolyzes both carnosine and anserine, preferring dipeptides that have a histidine monomer in the C-terminus position.[11][12] Tissue carnosinase is often considered a "nonspecific dipeptidase",[13][15] based in part on its ability to hydrolyze a range of dipeptide substrates, including those belonging to prolinase.[16]
2. Serum carnosinase:[14] This is the carnosinase found in the blood plasma. Deficiency of this form of carnosinase, along with carnosinuria ("carnosine in the urine"), is the usual metabolic indicator of systemic carnosinase deficiency.[3][8][17] Serum carnosinase is a glycoprotein, and splits free carnosine and anserine in the blood.[11] This form of the dipeptidase is not found in human blood until late infancy, slowly rising to adult levels by age 15.[14] Unlike tissue carnosinase, serum carnosinase also hydrolyzes the GABA metabolite homocarnosine.[11]Homocarnosinosis, a neurological disorder resulting in an excess of homocarnosine in the brain, though unaffected by tissue carnosinase, is caused by a deficiency of serum carnosinase in its ability to hydrolyze homocarnosine.[18]
A deficiency of tissue and serum carnosinase, with serum being an indicator, is the underlying metabolic cause of carnosinemia.[7][9]
^ abPerry TL, Hansens S, Tischler B, Bunting R, Perry K (1967). "Carnosinemia. A new metabolic disorder associated with neurological disease and mental defect". N. Engl. J. Med. 277 (23): 1219–1227. doi:10.1056/NEJM196712072772302. PMID6058610.
^Rashid I, van Reyk DM, Davies MJ (2007). "Carnosine and its constituents inhibit glycation of low-density lipoproteins that promotes foam cell formation in vitro". FEBS Lett. 581 (5): 1067–1070. doi:10.1016/j.febslet.2007.01.082. PMID17316626. S2CID46535145.
^ abcTerplan KL, Cares HL (1972). "Histopathology of the nervous system in carnosinase enzyme deficiency with mental retardation". Neurology. 22 (6): 644–655. doi:10.1212/wnl.22.6.644. PMID4673339. S2CID31717219.
^ abcWisniewski K, Fleisher L, Rassin D, Lassmann H (1981). "Neurological diseases in a child with carnosinase deficiency". Neuropediatrics. 12 (2): 143–151. doi:10.1055/s-2008-1059647. PMID7266778.
^Zschocke J, Nebel A, Wicks K, Peters V, El Mokhtari NE, Krawczak M, van der Woude F, Janssen B, Schreiber S (2006). "Allelic variation in the CNDP1 gene and its lack of association with longevity and coronary heart disease". Mech Ageing Dev. 127 (11): 817–820. doi:10.1016/j.mad.2006.08.002. PMID16965804. S2CID32393210.
^ abcdJackson MC, Kucera CM, Lenney JF (1991). "Purification and properties of human serum carnosinase". Clin Chim Acta. 196 (2–3): 193–205. doi:10.1016/0009-8981(91)90073-L. PMID1903095.
^Lenney JF, Peppers SC, Kucera CM, Sjaastad O (1983). "Homocarnosinosis: lack of serum carnosinase is the deficiency probably responsible for elevated brain and CSF homocarnosine". Clin Chim Acta. 132 (2): 157–165. doi:10.1016/0009-8981(83)90243-7. PMID6616870.