Abstract: Disclosed are compositions, systems, kits, and methods for detecting an analyte or target molecule in a sample by regulated in vitro transcription. The compositions, systems, kits, and methods typically comprise and/or utilize one or more components selected from: (a) an RNA polymerase; (b) an allosteric transcription factor (aTF), wherein the aTF binds an analyte or target molecule as a ligand; (c) an engineered transcription template; (d) a dsDNA signal gate molecule; (e) a dsDNA fuel gate molecule; and/or any combination thereof.

Abstract: An enzyme carnitinehydrolyase is isolated from microorganisms belonging to the family Enterobacteriaceae, particularly Escherichia coli, Proteus vulgarius, Proteus mirabilis, Citrobacter freundii, Salmonella typhimurium, Salmonella anatum, e Salmonella cottbus, following anaerobic cultivation of the microorganisms in the presence of D,L-carnitine and/or crotonobetaine, by cell disruption and chromatography of the resulting protein extract. The enzyme, upon immobilization and activation by an effector which is also obtained from the protein extract following enzyme isolation, is used for stereoselectively hydrating crotonobetaine into L(-)-carnitine by contacting a solution of crotonobetaine or crotonobetaine derivatives with carnitinehydrolyase in the presence of the effector.