TABLE 1.

Comparison of the biochemical properties of the pneumococcal and S. mitis phage amidases

Enzyme	Sp act, U 10−5/mg of protein (%)a	Optimum pH for activity	Activity after dialysis (%)b	Activity (%) after treatmentc with:		Choline 50% inhibitory concn (mM)d
				1% deoxycholate	1% Triton X-100	Deconverted	Converted
LytAR6	13.0 (100)	6.5	100	100	120	5	20
LytAB6	4.4 (33.8)	5.5	10	2	32	2	20
LytAHER	4.6 (35.4)	5.5	10	3	33	0.4	10
LytAR6(T)e	12.7 (100)	6.5	10	30	90	3	20

^aActivity values are the averages of at least three independent determinations with pneumococcal cell walls as the substrate. Each enzyme was assayed at its optimal pH (6.5 in 20 mM sodium phosphate buffer for LytA_R6 and 5.5 in 0.1 M sodium acetate for LytA_B6 and LytA_HER). The percentage of LytA_K6 activity is shown in parentheses.

^bEnzymes were dialyzed in the cold against the appropriate buffer for at least 3 h and assayed without any conversion step. Percentages were calculated with respect to the activity of the corresponding nondialyzed enzyme.

^cPercentages were calculated with respect to that of untreated LytA_R6.

^dFor LytA_R6, unconverted and converted mean crude E-form and purified C-form amidase, respectively, whereas for phage proteins those terms refer to dialyzed and dialyzed and then converted enzymes, respectively. Deconverted data for LytA_R6 are from a previous publication (8).

^eLytA_R6(T) is LytA_R6 in which Val₃₁₇ has been replaced by Thr.