Hartley J C, Vedamuthu E R
Appl Microbiol. 1975 Jan;29(1):74-80. doi: 10.1128/am.29.1.74-80.1975.
Ten strains of Propionibacterium shermanii were tested for beta-galactosidase (beta-gal) activity. Of these ten strains, five yielded enhanced enzyme activity when cell suspensions were treated with toluene-acetone; on solvent treatment, the remaining five lost a considerable portion of the activity found in whole-cell suspensions. By using a strain yielding decreased activity upon solvent treatment, explanations for the loss in activity were sought through assays for possible alternative beta-galactoside utilization mechanisms. When this strain was assayed for beta-D-phosphogalactoside galactohydrolase by using orthonitrophenyl-beta-D-galactopyranoside-6-P04 as a substrate, the activity was wither lower or indiffernt as compared with beta-gal activity determined simultaneously. Cell suspensions of P. shermanii 7 and 22 (strains chosen for further work) grown separately on the individual substrates (lactose, glucose, galactose, and sodium lactate) did not show significant differences in beta-gal activity. Optimal temperature for beta-gal activity in untreated and toluene-acetone-treated cell suspensions of strain 7 was 52 C. With strain 22, of the temperatures tested, maximal activity in untreated cell suspensions was noted at 58 C and with solvent-treated cells at 32 C. In the cell-free extract (CFE) system, both strains exhibited maximal activity at 52 C. Optimal pH for untreated and solvent-treated cell suspensions of both strains was around 7.5. In the P. shermanii 22 CFE system, maximal activity occurred at pH 7.0; pH had very little effect on enzyme activity in P. shermanii 7 CFE. Sodium or potassium phosphate buffers in the assay system yielded the best activity. In the CFE system of these two strains, Mn2+ was definitely stimulatory, but in untreated and solvent-treated cell systems of these strains presence or absence of Mn2+ in the assay system had variable effects on enzyme activity. Maximal beta-gal activity was noted in P. shermanii 7 cells harvested after 28 h of growth at 32 C in sodium lactate broth. Sulfhydryl-group blocking agents inhibited enzyme activity in P. shermanii 22 CFE; the inhibition was partly reversed by dithiothreitol.
对十株谢氏丙酸杆菌进行了β-半乳糖苷酶（β-gal）活性测试。在这十株菌中，有五株在用甲苯-丙酮处理细胞悬液后酶活性增强；经溶剂处理后，其余五株失去了全细胞悬液中相当一部分活性。通过使用一株经溶剂处理后活性降低的菌株，通过检测可能的替代β-半乳糖苷利用机制来寻找活性丧失的原因。当使用邻硝基苯基-β-D-吡喃半乳糖苷-6-磷酸作为底物检测该菌株的β-D-磷酸半乳糖苷半乳糖水解酶时，与同时测定的β-gal活性相比，其活性较低或无差异。分别在乳糖、葡萄糖、半乳糖和乳酸钠等单一底物上生长的谢氏丙酸杆菌7和22（选择用于进一步研究的菌株）的细胞悬液，其β-gal活性没有显著差异。菌株7未经处理和经甲苯-丙酮处理的细胞悬液中β-gal活性的最适温度为52℃。对于菌株22，在所测试的温度中，未经处理的细胞悬液在58℃时活性最高，经溶剂处理的细胞在32℃时活性最高。在无细胞提取物（CFE）系统中，两株菌在52℃时均表现出最大活性。两株菌未经处理和经溶剂处理的细胞悬液的最适pH约为7.5。在谢氏丙酸杆菌22 CFE系统中，最大活性出现在pH 7.0时；pH对谢氏丙酸杆菌7 CFE中的酶活性影响很小。测定系统中的磷酸钠或磷酸钾缓冲液产生的活性最佳。在这两株菌的CFE系统中，Mn²⁺肯定具有刺激作用，但在这些菌株未经处理和经溶剂处理的细胞系统中，测定系统中Mn²⁺的存在或不存在对酶活性有不同影响。在32℃的乳酸钠肉汤中生长28小时后收获的谢氏丙酸杆菌7细胞中，β-gal活性最高。巯基阻断剂抑制谢氏丙酸杆菌22 CFE中的酶活性；二硫苏糖醇可部分逆转这种抑制作用。
