TABLE 2.

Enzymes and substrates used in the study and recommended buffer pHs

Enzyme	General function	Substrate(s)	EC no.	Recommended assay pH
Phosphomonoesterase	Release of inorganic phosphate from simple phosphomonoesters, including organic and condensed inorganic phosphates	4-Methylumbelliferyl phosphate	3.1.3.2 (acid)	6.5a
			3.1.3.1 (alkaline)	11.0a
Phosphodiesterase	Release of a phosphate monoester from phosphodiesters	Bis-(4-methylumbelliferyl) phosphate	3.1.4.1	8.0a
Cellobiohydrolase (cellulose 1,4-β-cellobiosidase)	Hydrolysis of cellulose from plant cell walls	4-Methylumbelliferyl β-d-cellobiopyranoside	3.2.1.91	5.5b
β-Xylanase (xylan 1,4-β-xylosidase)	Hydrolysis of hemicellulose from plant cell walls	4-Methylumbelliferyl β-d-xylopyranoside	3.2.1.37
α-Glucosidase	Hydrolysis of α-glucosyl residues to release α-d-glucose	4-Methylumbelliferyl α-d-glucopyranoside	3.2.1.20	6.0c
β-Glucosidase	Hydrolysis of β-glucosyl residues to release β-d-glucose; the final step in cellulose hydrolysis	4-Methylumbelliferyl β-d-glucopyranoside	3.2.1.21	6.0a
N-Acetyl-β-glucosaminide (β-N-acetylhexosaminidase)	Hydrolysis of glycosidic (N-acetyl-β-glucosaminide) bonds in chitin	4-Methylumbelliferyl N-acetyl-β-d-glucosaminide	3.2.1.52	5.5d
Arylsulfatase	Release of inorganic sulfate from organic sulfate esters	4-Methylumbelliferyl sulfate, potassium salt	3.1.6.1	5.8a

^aRecommended by Tabatabai (51), with use of chromogenic substrates.

^bRecommended by Deng and Tabatabai (12) for cellulase, with use of a carboxymethyl cellulose substrate.

^cRecommended by Eivazi and Tabatabai (16), with use of a chromogenic substrate.

^dRecommended by Parham and Deng (35), with use of a chromogenic substrate.