Cleavage enzyme

Testiculat androgens are synthesized in the interstitial tissue by the Leydig cells. The immediate precursor of the gonadal steroids, as for the adrenal steroids, is cholesterol. The rate-limiting step, as in the adrenal, is delivery of cholesterol to the inner membrane of the mitochondria by the transport protein StAR. Once in the proper location, cholesterol is acted upon by the side chain cleavage enzyme P450scc. The conversion of cholesterol to pregnenolone is identical in adrenal, ovary, and testis. In the latter two tissues, however, the reaction is promoted by LH rather than ACTH. 

Carotene cleavage enzymes — Two pathways have been described for P-carotene conversion to vitamin A (central and eccentric cleavage pathways) and reviewed recently. The major pathway is the central cleavage catalyzed by a cytosolic enzyme, p-carotene 15,15-oxygenase (BCO EC 1.13.1.21 or EC 1.14.99.36), which cleaves p-carotene at its central double bond (15,15 ) to form retinal. Two enzymatic mechanisms have been proposed (1) a dioxygenase reaction (EC 1.13.11.21) that requires O2 and yields a dioxetane as an intermediate and (2) a monooxygenase reaction (EC 1.14.99.36) that requires two oxygen atoms from two different sources (O2 and H2O) and yields an epoxide as an intermediate. ... 

Wyss, A., Carotene oxygenases a new family of double bond cleavage enzymes, J. Nutr. 134, 246S, 2004. 

Buchan A, LS Collier, EL Neidle, MA Moran (2000) Key aromatic-ring-cleavage enzyme, protocatechuate 3,4-dioxygenase, in the ecologically important marine Roseobacter lineage. Appl Environ Microbiol 66 4662-4672. 

Lendenmann U, JC Spain (1996) 2-aminophenol 1,6-dioxygenase a novel aromatic ring cleavage enzyme purified from Pseudomonas pseudoalcaligenes JS 45. J Bacteriol 178 6227-6232. 

Gescher J, W Eisenreich, J Wort, A Bacher, G Fuchs (2005) Aerobic benzoyl-CoA catabolic pathway inAzoarcus evansii studies on the non-oxygenolytic ring cleavage enzyme. Mol Microbiol 56 1586-1600. 

Pelletier DA, CS Harwood (1998) 2-ketohexanecarboxyl coenzyme A hydrolase, the ring cleavage enzyme required for anaerobic benzoate degradation by Rhodopseudomonas palustris. J Bacteriol 180 2330-2336. 

Block DW, F Lingens (1992b) Microbial metabolism of qninoline and related compounds XIV. Purification and properties of lH-3-hydroxy-4-oxoquinoline oxygenase, a new extradiol cleavage enzyme from Pseudomonas putida strain 33/1. Biol Chem Hoppe-Seyler 370 343-349. 

Sato, S-I, N Ouchiyama, T Kunura, H Nojiri, H Yamane, T Omori (1997a) Cloning of gees involved in carbazole degradation of Pseudomonas sp. strain CAIO nucleotide sequences of genes and characterization of meta cleavage enzymes and hydrolase. J Bacteriol 179 4841-4849. 

Burbidge, A., T. Grieve et al. (1997). Structure and expression of a cDNA encoding a putative neoxanthin cleavage enzyme (NCE), isolated from a wilt-related tomato (Lycopersicon esculentum Mill.) library. J. Exp. Bot. 48(317) 2111-2112. 

Fleischmann, R, K. Studer et al. (2002). Partial purification and kinetic characterization of a carotenoid cleavage enzyme from quince fruit (Cydonia oblonga). J. Agric. Food Chem. 50(6) 1677-1680. 

Schwartz, S. H., X. Q. Qin et al. (2004). The biochemical characterization of two carotenoid cleavage enzymes from Arabidopsis indicates that a carotenoid-derived compound inhibits lateral branching. J. Biol. Chem. 279(45) 46940 16945. 

CYPUAl P450scc Cholesterol side-chain cleavage enzyme— Pregnenolone... 

Takase M, Ukena K, Yamazaki T, Kominami S, Tsutsui K. 1999. Pregnenolone, pregnenolone sulfate, and cytochrome P450 side-chain cleavage enzyme in the amphibian brain and their seasonal changes. Endocrinology 140 1936-1944. 

Ukena K, Usui M, Kohchi C, Tsutsui K. 1998. Cytochrome P450 side-chain cleavage enzyme in the cerebellar Purkinje neuron and its neonatal change in rats. Endocrinology 139 137-147. 

Tab. 10.1 Examples of endo-linkers and respective cleavage enzymes. 

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