SUBSTRATE SPECIFICITIES OF LICHENASE AND XYLANASES FROM ASPERGILLUS PHOENICIS
Zeng Yucheng Zhang Shuzheng(Institute of Microbiology, Academia Sinica, Beijing)
The substrate specificities of X-Ⅰ, X-Ⅱ and X-Ⅲ from Aspergillus phoenicis were investigated. X-Ⅰ showed the highest activity toward lichenin, the relative activity of X-Ⅰ toward lichenin, wheat bran hemicellulose H (HH) and B (HB) were 100, 32.9 and 12.8, respectively. Therefore X-Ⅰ was a lichenase (EC. 3.2. 1.73) with xylanase activity. X-Ⅱ showed higher activities toward oat spelts xy- lan, wheat bran HB and HH, and a somewhat lower activities toward lichenin and other xy- lans, so X-Ⅱ was a xylanase with lichenase activity. X-Ⅲ showed the highest activity to- ward larchwood xylan, high activities toward other xylans, but no activities toward lichenin, CMC and other β-glucans, so X-Ⅲ was a spe- cific xylanase. The Km of X-Ⅰ for wheat bran HB, X-Ⅱ for oat spelts xylan and X-Ⅲ for larcbwood xylan were 9.9, 2.1 and 1.8 mg/ml. The products of X-Ⅰ from various xylans were mainly xylooligosaccharides, no xylobiose, xy- lose and arabinose; and that of X-Ⅱ, X-Ⅲ were mainly xylobiose, and xylooligosacchari- des higher than xylobiose, with small amount of xylose and arabinose. X-Ⅱ produced more arabinose than xylose, and vice versa for X- Ⅲ.