| ordered on-random off mechanism | A scheme for substrate binding and product release for multisubstrate enzymes; for a two-substrate two-product enzyme with this mechanism, the individuals have to bind to the enzyme in a distinct order; however, once the products are formed they may dissociate from the enzyme in either order. It has been suggested that pyruvate kinase has such a mechanism. The random on-ordered off mechanism is simply the reverse of this mechanism. (05 Mar 2000) |
|---|---|
| all-trans-retinal | The orange retinaldehyde resulting from the action of light on the rhodopsin of the retina, which converts the 11-cis-retinal component of the rhodopsin to all-trans-retinal plus opsin. Synonym: trans-retinal, visual yellow. (05 Mar 2000) |
| peptidyl prolyl cis trans isomerase | See: PPIase and immunophilin. (18 Nov 1997) |
| cis-9,trans-11-octadecadienoate reductase | <enzyme> Uses NADH and alpha-tocopherol quinol; forms trans-11-octadecenoate Registry number: EC 1.3.1.- Synonym: 9,11-ocdd reductase (26 Jun 1999) |
| cis-trans-isomerases | <enzyme> Enzymes that catalyze the rearrangement of geometry about double bonds. Registry number: EC 5.2 (12 Dec 1998) |
| cis trans test | <molecular biology> The complementation test with two or more interacting genes placed in cis and in trans relationships to each other. A double mutant genome is used in the cis test made from the two single mutant genomes used in the trans test by recombination. If the wild type phenotype is restored by both cis and trans arrangements it is concluded that the two mutations are in different genes and hence that the phenotype is determined by more than one gene. If the trans test is negative and the cis positive this means that the two mutations are in the same gene. If both tests are negative then at least one of the mutations must be dominant. Thus the double test provides a means of fine mapping of genes. A lab test which is used to determine whether two mutations of different genes which affect the same phenotype are on the same functional unit (indicating a cis configuration of the mutated genes) or on different functional units (indicating a trans configuration of the mutated genes). (A functional unit can be a chromosome.) The test is done by mating an individual that has one of the mutations to an individual that has the other one, and observing whether their offspring have the mutant phenotype. If the offspring do not have the mutant phenotype, then the genes are known to be trans, because the offspring have normal copies of each mutant gene on the different functional units which are able to genetically complement each other. If the offspring do have the mutant phenotype, then the genes are known to be cis, because the offspring will always inherit at least one of the mutant genes on the one functional unit, resulting in the mutant phenotype. (09 Oct 1997) |
| trans- | 1. Prefix denoting across, through, beyond; opposite of cis-. 2. In genetics, denoting the location of two genes on opposite chromosomes of a homologous pair. 3. In organic chemistry, a form of geometric isomerism in which the atoms attached to two carbon atoms, joined by double bonds, are located on opposite sides of the molecule. 4. In biochemistry, a prefix to a group name in an enzyme name or a reaction denoting transfer of that group from one compound to another; e.g., transformylase (transfers a formyl group), transpeptidation. Origin: L. Trans, through, across (05 Mar 2000) |
| trans-1,2-dihydrobenzene-1,2-diol dehydrogenase | <enzyme> Rat liver cytosol enzyme also catalyses 3alpha-hydroxysteroid dehydrogenase activity (EC 1.1.1.50); bphb isolated from pseudomonas Registry number: EC 1.3.1.20 Synonym: acenaphthenol oxidase, dihydrodiol dehydrogenase, bphb gene product, biphenyl-2,3-dihydrodiol-2,3-dehydrogenase (26 Jun 1999) |
| trans-2-hydroxybenzylidenepyruvate hydratase-aldolase | <enzyme> Catalyses the hydration of cis-o-hydroxybenzylidenepyruvate with subsequent cleavage to form salicylaldehyde--important steps in the bacterial degradation of naphthalene to salicylate Registry number: EC 4.2.1.- Synonym: trans-o-hydroxybenzylidenepyruvate hydratase-aldolase, thbpa hydratase-aldolase (26 Jun 1999) |
| trans-3-chloroacrylic acid dehalogenase | <enzyme> Specific for conversion of trans-3-chloroacrylic acid to muconic saemialdehyde (3-oxopropionic acid); 34 amino-terminal amino acid sequence, with 3 questionable aas, given in first source Registry number: EC 3.8.1.- Synonym: trans-3caa dehalogenase (26 Jun 1999) |
| trans-4-coumaroyl esterase | <enzyme> From bacterial and fungal cultures; cleaves coumaric acid from plant cell wall polysaccharides; see also record for feruloyl-4-coumaroyl esterase Registry number: EC 3.1.1.- Synonym: trans-p-coumaroyl esterase, p-coumaroyl esterase, p-coumaric acid esterase (26 Jun 1999) |
| trans-activation (genetics) | Increased rate of gene expression directed by either viral or cellular proteins. These regulatory factors (diffusible gene products) act in trans -- that is, act on homologous or heterologous molecules of DNA. (cis-acting factors act only on homologous molecules.) (12 Dec 1998) |
| trans-activators | Diffusible gene products that act on homologous or heterologous molecules of viral or cellular DNA to regulate the expression of proteins. (12 Dec 1998) |
| trans-bronchial biopsy | <chest medicine, procedure> A biopsy that is performed through the wall of the bronchus (using the bronchoscope). This involves obtaining a small piece of lung tissue for microscopic analysis. This is a useful alternative to an open surgical biopsy, where an incision must be made. (17 Mar 1998) |
| trans configuration | 1. <chemistry> The configuration of an organic molecule containing a double bond between two carbon atoms, where the largest, most complex R groups attached to each carbon are on opposite sides. Alternatively: The configuration of an organic molecule containing a ring, where the largest, most complex R groups attached to each carbon are on opposite sides. These configurations are the opposite of cis configuration. 2. <genetics> A genetics term meaning that the changes in gene expression are due to something acting on the gene from a distance, or from an unrelated location, rather than on the same strand of DNA. Two mutations in different genes coding for the same phenotype which are on opposite homologous chromosomes (as opposed to the cis configuration where both of the mutations are on the same homologue). (17 Mar 1998) |