TABLE 1.

Recovery of M. tuberculosis β-lactamase during purification^a

Step	Total activityb	Sp actc	Purifi- cation factord	Yield (%)d
Broth supernatant	15,100	0.8
NH4SO4 precipitation	8,600	13	16	56
Gel filtration (G-75 Sephadex)	5,400	81	100	36
Chromatofocusing	4,080			26
Peak 1	400	370	462	2.6
Peak 2	3,200	1,600	2,000	21.2
Peak 3	480	700	875	3.2
Anion exchange	3,800	580	725	25

^aValues represent the average of six experiments. After gel filtration, the β-lactamase was purified further by either chromatofocusing (four experiments) or anion-exchange chromatography (two experiments). 

^bTotal activity is reported as nanomoles of nitrocefin degraded per minute in 0.1 M sodium phosphate buffer (pH 6.0) at 37°C. 

^cSpecific activity determinations are reported as nanomoles of nitrocefin degraded per minute per milligram of protein. Protein concentrations were determined spectrophotometrically assuming an extinction coefficient at 280 nm of 1.0 for the protein. 

^dPurification factor and percent yield are relative to the values for the broth supernatant.