Abstract: A protein having luciferase activity and at least 60% similarity to luciferase from Photinus pyralis, Luciola mingrelica, Luciola cruciata or Luciola lateralis.

Abstract: The use of an assay for adenylate kinase in an in vitro test for the effect of external conditions on the growth characteristics of bacterial cells. Such tests in particular include tests for the sensivity of a bacteria to an antibiotic or a biostatic agent, and tests to assess the growth stage and health of the bacteria. Methods of carrying out these tests and kits for effecting them are also described and claimed.

Abstract: A method for producing a polypeptide product which is substantially free of an undesired protein, the process comprising culturing a host cell which is able to express said polypeptide product and which is able to express said undesired protein only in a mutant form which form has the activity of the corresponding native protein under culture conditions but is unstable under conditions at which the said polypeptide product remains stable; and recovering the desired product, wherein either the host cell culture or the recovered product is subjected for a sufficient period of time to conditions under which the undesired protein is unstable so as to denature the undesired protein The method allows the production of products which are substantially free of particular undesired contaminants.

Abstract: Proteins are provided having luciferase activity with lower Km than wild-type luciferases by altering the amino acid residue at position 270 of the wild-type to an amino acid other than glutamate. Greater heat stability than wild-type luciferases while retaining the lower Km is provided by also replacing the glutamate equivalent to that at position 354 of Photinus pyralis luciferase or 356 of Luciola luciferases with an alternative amino acid, particularly lysine and/or the amino acid residue at 215 of Photinus pyralis and 217 of the Luciola species with a hydrophobic amino acid. DNA, vectors and cells that encode for and express the proteins are also provided as are test kits and reagents for carrying out luminescence assays using the proteins of the invention.