The Diel Patterns of Glucosidase Activity and Dissolved Carbohydrates in South Florida Coastal Waters

• Main Author: Quinney, Tom
• Published: NSUWorks 1998
• Subjects: Marine Biology; Oceanography and Atmospheric Sciences and Meteorology
• Online Access: http://nsuworks.nova.edu/occ_stuetd/324

The response of diel extracellular α and β-glucosidase activity to in situ dissolved carbohydrates was explored in coastal marine waters. The hypothesis being tested was to determine whether natural substrate could regulate enzyme activity. Relative enzyme activity was determined using artificial 4-methylumbelliferone (MUF) substrate derivatives at low substrate concentrations (300 nM). Disssolved carbohydrate concentrations were measured using the 3-methyl-2-benzothlazolinone hydrazone hydrochloride (MBTH) method: a spectrophotometric determination of monosaccharide concentrations. Six studies were conducted and p-glucosidase activity (BOA) was found to be positively correlated with dissolved polysaccharide concentrations (PCHO) in two studies which suggests that PCHO can potentially regulate BOA. A significant inverse correlation (Spearman) between dissolved monosaccharides (MCHO) and β-glucosidase activity was found in one study suggesting that MCHO was capable of repressing and/or inhibiting the activity of β-glucosidase under some conditions. Three significant positive relationships were found between α-glucosidase (AOA) and BOA suggesting that there was a tight coupling between substrate release and hydrolysis. No obvious relationships were found between hydrolytic enzymes and dissolved carbohydrates in three diel studies. This may have been due to uncontrollable factors such as nutrient limitation, grazing and the inability to distinguish between α- and β-glucans. Combined data for PCHO and BOA showed an inverse relationship suggesting that high levels of naturally occurring PCHO may compete with MUF-β-glucans for β-glucosidase active sites causing a lower rate of MUF-β-glucan hydrolysis.