Polysaccharide isolated from Glycyrrhiza uralensis Fisch induces intracellular enzyme activity of macrophages

Predicting the pattern of soil organic matter (SOM) decomposition as a feedback to climate change, via release of CO2, is extremely complex and has received much attention. However, investigations often do not differentiate between the extracellular and intracellular processes involved and work is needed to identify their relative temperature sensitivities. Samples were collected from a grassland soil at Sonning, UK with average daily maximum and minimum soil temperature of 15 &#176;C and 5 &#176;C. We measured potential activities of &#946;-glucosidase (BG) and chitinase (NAG) (extracellular enzymes) and glucose-induced CO2 respiration (intracellular enzymes) at a range of assay temperatures (5 &#176;C, 15 &#176;C, 26 &#176;C, 37 &#160;&#176;C, and 45 &#176;C). The temperature coefficient Q10 (the increase in enzyme activity that occurs after a 10 &#176;C increase in soil temperature) was calculated to assess the temperature sensitivity of intracellular and extracellular enzymes activities. Between 5 &#176;C and 15 &#176;C intracellular and extracellular enzyme activities had equal temperature sensitivity, but between 15 &#176;C and 26&#176;C intracellular enzyme activity was more temperature sensitive than extracellular enzyme activity and between 26 &#176;C and 37 &#176;C extracellular enzyme activity was more temperature sensitive than intracellular enzyme activity. This result implies that extracellular depolymerisation of higher molecular weight organic compounds is more sensitive to temperature changes at higher temperatures (e.g. changes to daily maximum summer temperature) but the intracellular respiration of the generated monomers is more sensitive to temperature changes at moderate temperatures (e.g. changes to daily mean summer temperature). We therefore conclude that the extracellular and intracellular steps of SOM mineralisation are not equally sensitive to changes in soil temperature. The finding is important because we have observed greater increases in average daily minimum temperatures than average daily mean or maximum temperatures due to increased cloud cover and sulphate aerosol emission. Accounting for this asymmetrical global warming may reduce the importance of extracellular depolymerisation and increase the importance of intracellular catalytic activities as the rate limiting step of SOM decomposition.

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G-6-PD Long Prairie: a new glucose-6-phosphate dehydrogenase mutant exhibiting normal sensitivity to inhibition by NADPH and accompanied by nonspherocytic hemolytic anemia

Blood ◽

10.1182/blood.v49.2.247.247 ◽

1977 ◽

Vol 49 (2) ◽

pp. 247-251 ◽

Cited By ~ 10

Author(s):

GJ Johnson ◽

ME Kaplan ◽

E Beutler

Keyword(s):

Enzyme Activity ◽

Enzymatic Activity ◽

Alternative Mechanism ◽

Ph Optimum ◽

Intracellular Enzyme ◽

Chronic Hemolysis ◽

Increased Sensitivity ◽

Normal Sensitivity ◽

Glucose 6 Phosphate Dehydrogenase ◽

Heat Instability

Abstract The enzymatic properties of a new glucose-6-phosphate dehydrogenase (G- 6-PD) variant (G-6-PD Long Prairie) were studied in a white patient with chronic nonspherocytic hemolysis. The red cells were found to have 2.3%-7.7% normal enzymatic activity. The mutant enzyme exhibited marked heat instability, an increased pH optimum, a moderately decreased Km for G-6-P, and increased utilization of 2-deoxyglucose-6-phosphate and deamino NADP. The Km for NADP and Ki for NADPH were both normal. G-6-PD Long Prairie is an interesting new G-6-PD variant that demonstrates that chronic hemolysis can be associated with modestly decreased G-6-PD activity despite normal sensitivity to inhibition by NADPH. Although increased sensitivity to inhibition by NADPH has been postulated to decrease intracellular enzyme activity, resulting in enhanced susceptibility to hemolysis in certain G-6-PD variants with only moderately decreased enzymatic activity, an alternative mechanism of hemolysis, possibly enzyme thermolability, exists in G-6-PD Long Prairie.

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