Mode of action and properties of xylanase and β‐Xylosidase from Neurospora crassa

Abstract

Extracellular beta-xylosidase (1,4-beta-D-xylan xylohydrolase, EC 3.2.1.37) from culture filtrates of Neurospora crassa was purified to homogeneity by preparative isoelectric focusing followed by gel electrophoresis. The molecular weight of the purified xylosidase was 83,000 D and the K(m) on p-nitrophenyl-beta-D-xyloside was 0.047mM. The homogeneous xylanase (1,4-beta-D-xylan xylanohydrolase, EC 3.2.1.8) and beta-xylosidase showed differences in their mode of action towards xylooligosaccharides. The degree of hydrolysis of D-xylan by xylanase of N. crassa was 18%. Supplementation of beta-xylosidase from the same organism resulted in 48% hydrolysis. The synergistic effect was more pronounced, with the hydrolysis of 68%, when a homogeneous preparation of beta-xylosidase from Sclerotium rolfsii was added to the saccharification system.

Purification and Characterization of a Thermostable -Xylosidase from Thermomonospora fusca

“…These values are in accord with the apparent K , published for the crude P-xylosidase activity of a different Thermomonospora strain (Ristroph & Humphrey, 1985). The Neurospora crassa and Aspergillus P-xylosidases show a greater affinity for this substrate than the T. fusca enzyme, with apparent K , values of 0-05 mM and 0.22 mM respectively (Deshpande et al, 1986;John et al, 1979). However, other bacterial and fungal enzymes studied show less affinity for this substrate than the T. fusca enzyme.…”

“…The pxylosidase of T. fusca is therefore more acidic than the other bacterial /?-xylosidases described (Kersters-Hilderson et af., 1969; Lee & Forsberg, 1987), but is similar in PI to those produced by fungi (Deshpande et al, 1986;Matsuo & Yasui, 1984;Takenishi et al, 1973).…”

“…Furthermore, the Q-xylosidase of Clostridium acetobutylicum is also described as having a trimeric structure, although heterogeneous, comprising one 63 kDa and two 85 kDa subunits (Lee & Forsberg, 1987). In contrast, the /?-xylosidases of fungi described to date are monomeric proteins of lower molecular masses, in the range 83-102 kDa (Deleyn et al, 1978;Deshpande et al, 1986;Matsuo & Yasui, 1984).…”

“…This activity has been described in a wide range of micro-organisms, including actinomycetes (Dekker & Richards, 1976;McCarthy, 1987). More recently, the involvement of arabinofuranosidase, a-glucuronidase, P-xylosidase and various esterases has been studied (Biely, 1985 ; MacKenzie et af., 1987 ;Puls et af., 1987) and various enzyme combinations have been shown to act synergistically (Biely et al, 1986 ;Deshpande et al, 1986). /I-Xylosidase (EC 3.2.1 .37 ; 1,497-D-xylan xylohydrolase) activity generates D-XylOSe from short-chain oligosaccharides and xylobiose and plays a crucial role in the relief of end-product inhibition of endoxylanase activity by xylobiose (Reilly, 1981).…”

Xylanases of Microorganisms

“…Òîìó ó äåÿêèõ гðèá³â, ÿê³ ðîñòóòü íà êñèëàí³, íå çàáðóäíåíîìó öåëþëîçîþ, ïðè íèçüêèõ ñï³ââ³äíîøåííÿõ àçîò/âóгëåöü â ñåðåäîâèù³ ìîжóòü ïðîäóêóâàòèñÿ êñèëàíîë³òè÷í³ фåðìåíòè, ÿê³ â³ëüí³ â³ä öåëþëàç. Îäíàê, âñòàíîâëåíî, ùî öåëþëîçîë³òè÷í³ ñóáñòðàòè º íåîáõ³äíèìè äëÿ ìàêñèìàëüíî¿ ïðîäóêö³¿ êñèëàíàçè Thermomonospora curvata [49], Neurospora crassa [15], Clostridium stercorarium [8]. ßê áóëî âñòàíîâëåíî [36], äåøåâ³ гåì³öåëþëîçí³ ñóáñòðàòè, òàê³ ÿê êóêóðóäçÿí³ êà÷àíè, ïøåíè÷í³ ³ ðèñîâ³ âèñ³âêè, ðèñîâà ñîëîìà, êóêóðóäçÿí³ ñòåáëà º íàéá³ëüø ïðèäàòíèìè äëÿ óòâîðåííÿ êñèëàíàç òàêèìè ì³êðîîðгàí³çìàìè ÿê Aspergillus awamori, Penicillium purpurogenum [28], Bacillus sp.…”