The enzymes, as Beatty1 defines them, are the catalysts of living organisms, and are divided into two groups: ectoenzymes and endoenzymes. The former, excreted from cells into the surrounding medium, can be detected by their characteristic properties, and the latter contained only in the cells, have to be extracted by special means.
As to the method of detection of bacterial ectoenzymes, the auxanographic method of Beijerinck seems to be the simplest. The method consists in mixing agar with any substance that can be used to detect bacterial ectoenzymes. The mixture is then inoculated with the organism, plated and incubated at 37 C., and the plate studied carefully after incubation. The presence of bacterial ectoenzymes may be shown by a zone of digestion or other change around the colonies. This zone usually appears clear and wide. By this method, Bijkman2 and Buxton3 demonstrated amylase, lipase, casein-splitting enzyme, etc.,
TONGS MS. ECTOENZYMES OF STREPTOCOCCI. JAMA. 1919;73(17):1277–1279. doi:10.1001/jama.1919.02610430025009
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