Lyase

Cysteine Conjugate-Beta Lyase Cytoplasmic also known as CCBL1 is a member of the class-I pyridoxal-phosphate-dependent aminotransferase family. CCBL1 catalyzes the irreversible transamination of the L-tryptophan metabolite L-kynurenine to form kynurenic acid (KA) it also metabolizes the cysteine conjugates of certain halogenated alkenes and alkanes to form reactive metabolites. Furthermore, CCBL1 catalyzes the beta-elimination of S-conjugates and Se-conjugates of L-(seleno) cysteine, resulting in the cleavage of the C-S or C-Se bond.

Serine racemase (SRR) is an enzyme which generates D-serine from L-serine. D-serine functions as a neuronal signaling molecule by activating NMDA receptors in the brain. Mammalian SRR is a pyridoxal 5'-phosphate dependent enzyme which catalyzes both the racemization of L-serine to D-serine and also the elimination of water from L-serine, producing pyruvate and ammonia. The SRR enzyme is physiologically stimulated by divalent cations (e.g., magnesium) and is allosterically activated by the magnesium/ATP complex.

N-acetylneuraminate lyase (NPL) is an enzyme which catalyzes the chemical reaction (N-acetylneuraminate ->N-acetyl-D-mannosamine + pyruvate). NPL is a member of a family of lyases, specifically the oxo-acid-lyases, which cleave carbon-carbon bonds. NPL participates in amino sugars metabolism.

Argininosuccinate lyase (ASL) is a member of the lyase 1 family. ASL is an enzyme which catalyzes the reversible breakdown of Argininosuccinate (ASA) yielding the amino acids arginine and fumarate. ASL which is located in the liver cytosol is the 4th enzyme of the urea cycle and involved in the biosynthesis of arginine in all species and the production of urea in ureotelic species. While Argininosuccinate synthetase (ASS) catalyzes the formation of argininosuccinate from citrulline and aspartate, ASL breaks down the newly formed argininosuccinate into L-arginine and fumarate. L-arginine continues within the urea cycle to form urea and orinthine, whereas fumarate can enter the citric acid cycle. ASL gene Mutations result in the autosomal recessive disorder argininosuccinic aciduria, or argininosuccinic acid lyase deficiency.

N-acetylneuraminate lyase (NanA) is a member of a family of lyases, specifically the oxo-acid-lyases, which cleave carbon-carbon bonds. NanA catalyzes the cleavage of N-acetylneuraminic acid (sialic acid) to form pyruvate and N-acetyl-D-mannosamine. NanA is inhibited by reduction with NaBH4 in the presence of the substrate, which indicates that it belongs to the Schiff-base-forming Class I aldolases. NanA is strongly inhibited by Cu2+ ions, p-chloromercuribenzoate and N-bromosuccinimide, it is also inhibited competitively by the reaction product, pyruvate, and its structurally related compounds, dihydroxyacetone and DL-glyceraldehyde.

Hydroxymethylglutaryl-CoA lyase (HMGCL) is a mitochondrial matrix protein which is a member of the HMG-CoA lyase family. HMGCL is a homodimer and participates in leucine catabolism and ketogenesis, the hepatic synthesis of ketone bodies which, during fasting, provides a major source of energy for the heart, brain and kidney. More precisely, HMGCL catalyzes the final step of these processes, the cleavage of 3-hydroxy-3-methylglutaryl-CoA to acetoacetic acid and acetyl-CoA.

Hydroxymethylglutaryl-CoA lyase (HMGCL) is a mitochondrial matrix protein which is a member of the HMG-CoA lyase family. HMGCL is a homodimer and participates in leucine catabolism and ketogenesis, the hepatic synthesis of ketone bodies which, during fasting, provides a major source of energy for the heart, brain and kidney. More precisely, HMGCL catalyzes the final step of these processes, the cleavage of 3-hydroxy-3-methylglutaryl-CoA to acetoacetic acid and acetyl-CoA.

Adenylosuccinate lyase (ADSL) is an enzyme which converts adenylosuccinate to AMP and fumarate as part of the purine nucleotide cycle. ADSL is involved in both de novo synthesis of purines and formation of adenosine monophosphate from inosine monophosphate. ADSL catalyzes 2 reactions in AMP biosynthesis: the removal of a fumarate from succinylaminoimidazole carboxamide (SAICA) ribotide to yield aminoimidazole carboxamide ribotide (AICA) and removal of fumarate from adenylosuccinate to yield AMP. Defects in the ADSL are the cause of adenylosuccinase deficiency (ADSL deficiency). ADSL deficiency is an autosomal recessive disorder distinguished by the accumulation in the body fluids of succinylaminoimidazole-carboxamide riboside (SAICA-riboside) and succinyladenosine (S-Ado). Adenylosuccinase deficiency results in succinylpurinemic autism, psychomotor retardation, and in some cases, growth retardation associated with muscle wasting and epilepsy.

Cystathionine gamma-lyase or cystathionase (CTH) is a member of the trans-sulfuration enzymes family. CTH is an enzyme which breaks down cystathionine into cysteine and alpha-ketobutyrate. The CTH catalyzes the last step in the transsulfuration pathway from methionine to cysteine. Glutathione synthesis in the liver is dependent upon the availability of cysteine. Mutations in the CTH gene cause cystathioninuria.