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Thyroid Peroxidase (TPO) represents one of the main autoantigenic targets in autoimmune thyroid disease of humans. Its identity with the formerly so-called `microsomal antigen` has been shown several years ago. As an integral membrane glycoprotein it is restricted to the apical plasma membrane of the follicular epithelial cells and comprises two identical subunits of approx. 100 kDa molecular weight. The hemoprotein TPO plays a key role in the thyroid hormone biosynthesis by catalysing both the iodination of tyrosyl residues and the coupling of iodotyrosyl residues in thyroglobulin (TG) to form precursors of the thyroid hormones T4 and T3.

Paraoxonase-1 or PON1 is part of the paraoxonase group of proteins. PON1 is an enzyme, responsible to the toxic metabolites of a different of organophosphorus insecticides hydrolyzation. Furthermore, PON1 is a dominant anti-atherosclerotic part of HDL. The enzyme needs PPAR-gamma for activation, leading to synthesis and release of paraoxonase 1 from the liver tissue, resulting in atherosclerosis reduction. PON1 has many qualities for atheroprotective through inflammatory lipid peroxides metabolism. This enzyme can hydrolyze a large number of substrates, for example cyclic carbonates, lactones, nerve gases etc.

Acy1 or Aminoacylase1 is a cytosolic, homodimeric, zinc-binding enzyme which catalyzes the hydrolysis of acylated L-amino acids to L-amino acids and acyl group, and has been suggested to operate in the catabolism and salvage of acylated amino acids. ACY1 is localized in chromosome 3p21.1, a region reduced to homozygosity in small-cell lung cancer (SCLC), and its expression has been observed to be reduced or undetectable in SCLC cell lines and tumors.

MUTM is a base excision repair enzyme that identifies and eliminates a large variety of oxidized purines from correspondingly impaired DNA. MUTM is nondismissable and essential to remove quickly its substrate lesions on the chromosome. MUTM, additionally, mends a large number of the lesions recognized by Endo III, signifying that MUTM takes a prominent part in the overall repair of both purine damage and pyrimidine damage in vivo.

Betaine-homocysteine methyltransferase (BHMT) is a cytosolic enzyme that catalyzes the conversion of betaine and homocysteine to dimethylglycine and methionine, respectively. BHMT displays differential expression in a model of liver cirrhosis.

ASS1 is involved in the urea cycle, which is a sequence of chemical reactions that is localized in liver cells. The urea cycle processes excess nitrogen that is generated as the body uses proteins. The surplus nitrogen is used to create a molecule called urea, which is excreted from the body in urine.

HEXA is the alpha subunit of the lysosomal enzyme beta-hexosaminidase which, combined with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules having N-acetyl hexosamines terminus. The two subunits composing Beta-hexosaminidase, alpha and beta, belong to the glycosyl hydrolases family and are encoded by distinct genes. Alpha subunit gene mutations can cause Tay-Sachs disease (GM2-gangliosidosis type I).

HNMT is located in the cytosol and uses S-adenosyl-L-methionine as the methyl donor. In the mammal’s brain,N(tau)-methylation controls the neurotransmitter activity of histamine since diamine oxidase is not located in the central nervous system. A well known genetic polymorphism influences the activity levels of HNMT gene product in red blood cells. HNMT inactivates histamine by n-methylation. HNMT is involved in degrading histamine and in regulating the airway response to histamine. Histamine is involved in regulation and modulation of immune response through the stimulation of four distinct subtypes of receptors, H1, H2, H3, and H4, that present on the target cells. Histamine is inactivated by the histamine-metabolizing enzyme HNMT in bronchus, kidney, and the central nervous system.

Acyl-coenzyme A thioesterase 13 (ACOT13) belongs to the thioesterase subfamily of esterase family. ACOT13 is highly expressed in the kidney with moderate expression in the brain, liver and intestines. ACOT13 contains a hotdog-fold and is thought to co-localize with microtubules, possibly having a role in cellular proliferation events. Deletion of a segment of the q arm of chromosome 6 is linked to early onset intestinal cancer, suggesting the presence of a cancer susceptibility locus.

Betaine-Homocysteine Methyltransferase 2 (BHMT2) is involved in the regulation of homocysteine metabolism. Homocysteine is a sulfur-containing amino acid which has a key role in methylation reactions. Transfer of the methyl group from betaine to homocysteine generates methionine, which donates the methyl group to methylate DNA, proteins, lipids, and other intracellular metabolites. BHMT2 is one of two methyl transferases which can catalyze the transfer of the methyl group from betaine to homocysteine. BHMT2 converts homocysteine to methionine using S-methylmethionine (SMM) as a methyl donor. Homocysteine metabolism anomalies are implicated in disorders varying from vascular disease to neural tube birth defects such as spina bifida.

GLO1 is involved in the catalysis and formation of S-lactoyl-glutathione from methylglyoxal condensation and reduced glutatione. GLO1 is linked to HLA and is localized to 6p21.3-p21.1, between HLA and the centromere. GLO1 enzyme is ubundantly expressed and present in numerous tumor cell lines, in which its concentration is often upregulated ubiquitisly. GLO1 is a major susceptible gene for autism in an ethnic Chinese population from Taiwan. GLO1 might be involved in the pathophysiology of mood disorders. GLO1 plays a role in the pathophysiology of mood disorders. Overexpression of GLO1 is associated with kidney tumor.

Pyrroline-5-Carboxylate Reductase Like (PYCRL) is a member of the pyrroline-5-carboxylate reductase family and acts as a homodecamer. PYCRL plays a key role in proline bio-synthesis. Proline serves as a non-enzymatic antioxidant to reduce damage caused by reactive oxygen species (ROS) in microorganisms, animals and plants. In the final stage of proline biosynthesis, PYCRL catalyzes the reduction of aldehyde dehydrogenase 4A1 (ALDH4A1) to proline with NAD(P)H as the cofactor.

SAT-1 is a member the acetyltransferase family, and is a rate-limiting enzyme in the catabolic pathway of polyamine metabolism. SAT1 catalyzes the acetylation of spermidine and spermine, and is involved in the regulation of the intracellular concentration of polyamines and their transport out of cells. Therefore, SAT-1’s role is essential in polyamine homoeostasis, given that acetylated products are either excreted from the cell or oxidized by acetylpolyamine oxidase. Increased SAT1 activity causes variety of other effects which include pancreatic cells death, obstruction of regenerative tissue growth, behavioral changes, keratosis follicularis spinulosa decalvans (KFSD), and hair loss.
Defects in the SAT1 gene are linked to KFSD (keratosis follicularis spinulosa decalvans), which is a rare X-linked disorder affecting the skin and the eye. The KFSD affected men show thickening of the skin of the neck, ears, and extremities, particularly the palms and soles, loss of eyebrows, eyelashes and beard, thickening of the eyelids with blepharitis and ectropion, and corneal degeneration. Even though the majority of the affected families are compatible with an X-linked inheritance, KFSD are found to be clinically and genetically heterogeneous.

AK4 belongs to the adenylate kinase family of enzymes. AK4 protein is restricted to the mitochondrial matrix. Adenylate kinases regulate the adenine and guanine nucleotide structures in a cell by catalyzing the reversible transfer of phosphate group among these nucleotides. Hereditary mutations which cause AK4 deficiencies in erythrocytes have been associated to hemolytic anemia.

Phosphoglucomutase-1 also known as PGM1 is a member of the phosphohexose mutase family. There are more than a few PGM isozymes, which catalyze the transfer of phosphate between the 1&6positions of glucose. In nearly all cell types, PGM1 isozymes predominate, representing around 90% of total PGM activity. It has been found that defects in PGM1 are the cause of glycogen storage disease type 14.

Glucosidase Beta Acid 3, also known as GBA3, hydrolyzes various types of glycosides. GBA3 takes part in a nonlysosomal catabolic pathway of glycosylceramide. GBA3 is a protein coding gene which acts as beta-glycosylceramidase.

Glycogenin-1 (GYG1) is an enzyme involved in glycogen biosynthesis. GYG1 is the chief enzyme involved in glycogen polymerisation. Glycogenin-1 is vital for the function of self-glucosylates, using an inter-subunit mechanism, to form an oligosaccharide primer which acts as substrate for glycogen synthase. In addition, GYG1 has a role in regulating glycogen metabolism and the achievement of maximal glycogen levels in skeletal muscle. GYG1 mRNA and protein content and activity increase in the muscle during recovery from prolonged and exhaustive exercise. GYG1 is inactivated with glycogen catabolism which concurs with an increase in glycogenin gene expression as exercise and glycogenolysis advance. Glycogenin will remain covalently attached to the reducing end of the glycogen molecule.

DCTPP1, also known as dCTP pyrophosphatase 1, contains an epilepsy-associated repeat (EAR) domain that is predicted to participate in protein-protein interactions, most likely involved in ligand recognition. This protein functions to hydrolyze abnormal nucleotide triphosphates (NTPs) in cancer cells that, if unregulated, could be incorporated into nascent DNA or RNA.

NAT6 is an enzyme that catalyzes the transfer of acetyl groups from acetyl-CoA to acrylamines. NAT6 is located mainly in the cytoplasm and its activity has been recognized by its feasibility to acetylate the N-terminus of proteins using a ping-pong-like mechanism and by its substrate specificity. Given that the NAT6 gene maps to the chromosomal region 3p21.3, which includes at least one tumor suppressor gene, the function of NAT6 plays an important role in cancer.

TDO2 is a ferrous heme enzyme that catalyzes the first and rate-limiting step in the kynurenine pathway which is the major pathway of tryptophan metabolism. TDO2 integrates oxygen into the indole moiety of tryptophan. TDO2 has broad specificity towards tryptamine and derivatives including D- and L-tryptophan, 5-hydroxytryptophan and serotonin.

Short/branched chain specific acyl-CoA dehydrogenase (ACADSB) belongs to the acyl-CoA dehydrogenase family of enzymes which catalyze the dehydrogenation of acyl-CoA derivatives in the metabolism of fatty acids or branch chained amino acids. ACADSB catalyzes the degradation of L-isoleucine while having the highest affinity for (s)-2-methylbutyryl-CoA, isobutyryl-CoA and 2-methylhexanoyl-CoA as substrates. ACADSB may use valproyl-CoA as substrate. ACADSB gene defects cause the short/branched-chain acyl-CoA dehydrogenase deficiency (SBCADD), which is an autosomal recessive disorder characterized by an increase of 2-methylbutyrylglycine and 2-methylbutyrylcarnitine in blood and urine.

SENP8 is a cysteine protease which belongs to the sentrin-specific protease family. SENP8 takes part in processing and deconjugation of the ubiquitin-like protein labeled, neural precursor cell expressed developmentally downregulated 8(NEDD8).

Aminoacyl-tRNA synthetases are a class of enzymes which charge tRNAs with their cognate amino acids. Asparaginyl-tRNA synthetase (NARS) is localized to the cytoplasm and is a member of the class II family of tRNA synthetases. The N-terminal domain characterizes the signature sequence for the eukaryotic asparaginyl-tRNA synthetases.