Photometric Determination of Lysozyme Activity.

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Abstract
An accurate photometric method was developed using a Pfaltz and Bauer Fluorophotometer for measuring the lysis of suspensions of Micrococcus lysodiekticus by lysozyme. The procedure consists of pipetting 5 ml of the bacterial suspension (28 mg% dried cells obtained from liquid medium in pH 6.2 phosphate buffer, [image]/15); adding 0.5 mi enzyme solution and recording percent transmission every 30 seconds for 300 seconds. The activity increment (at 645 m[mu]) between 30 and 60 seconds, produced a straight line between the levels of 0 and 20 ug of the enzyme. A sensitive galvanometer was used which facilitated reproduction of results to [plus or minus] 0.2% transmission. Reliability of the assay appears to be 5 - 10%. Measurements can be reproduced 60 seconds after the addition of the enzyme. This method was applied to mammalian tissue extracts. Kidney appears to have the greatest concentration of lytic enzyme of the tissues tested. Measurement of the maximal rate of lysis in the early part of the time-course of reaction decreases the possibility of interference due to synergism by proteolytic enzymes or solution of cellular material by alkali reaction.