PAES

P. Grunow, H. Paes, C. Gatts, W. Losch, Thin Solid. Films 27S (1996) 191-194. 

PAe., abbrev. (Petroleumather) petroleum ether, paginieren, v.t. page, paginate. 

The same enzyme (RGAE) could be purified from A. niger, together with two other esterases a feruloyl esterase (FAE) and an acetyl esterase (PAE) specific for the removal of one type of acetyl group present in the smooth regions of sugar-beet pectin. 

Making use of the chromatographic methods mentioned above, two different acetyl esterases could be purified from AEI. These esterases were named PAE and FAE. A third esterase was purified from AEII and this esterase was named RGAE, since it appeared to be similar to the... 

Fig. 6. Points of attack of RGAE on acetyl esters in MHR (upper part) and possible points of attack of PAE on acetyl esters in beet pectin (see text for explanation).

For apple maceration, the main activity is the endopectinlyase (PL) which decreases the viscosity due to the colloidal pectin by decreasing tlie molecular weight of this substrate methylated at about 90%. In association to this PL, exo B and endoarabanase (ARAs), pectinacetylesterase (PAE), rhamnogalacturonase (RG) and other hemicellulases allow to hydrolyse side chains of the pectin, decrease the steric hindrance and make the access of pectinases to the rhamnogalacturonic backbone more easy. 

Acetyl esterases with different specificity occur in one Aspergillus niger preparation. Three acetyl esterases were purified and characterised pectin acetyl esterase (PAE), feruloyl acetyl esterase (FAE) and rhamnogalacturonan acetyl esterase (RGAE). 

Only PAE, a novel acetyl esterase, could remove acetyl from beet pectin, to a maximum of 30%. This was shown to be one specific acetyl group in theJiomogalacturonan chain of pectin (smooth region) by NMR spectroscopy. PAE activity was influenced by buffer salts and the addition of bivalent cations. PAE worked cooperatively with pectolytic enzymes. 

Contrary to PAE, RGAE removed at random the acetyl esters from apple pectic hairy ramified regions (MHR), to a maximum of 70 %. RGAE was essential for the activity of rhamnogalacturonase (RG), and as such comparable with A. aculeatus RGAE. 

The characteristics of the purified enzymes are summarised in Table 1. PAE was the only enzyme able to remove acetyl from beet pectin, FAE showed the highest activity towards... 

This novel enzyme was the only esterase able to release acetyl from sugar beet pectin and removed about 30% of the total acetyl groups present. It also caused the release of acetyl groups from a range of other acetylated substrates, either synthetic or extracted from plants, in small amounts. PAE had an apparent molecular weight of 60 kDa and showed optimal activity at pH 5.5 and a temperature of 50 C. The enzyme is sensitive to buffer composition and requires a bivalent cation for optimal activity and stability. In purified form this enzyme proved unstable, especially in phosphate buffers. 

A decrease in the pectic molecular weight by pectin lyase resulted in an increase in the activity of PAE (Figure 2). This could be caused by easier access of the enzyme to the substrate, but PAE is not limited in its action by the substrate size as was found for FAE. 

The effect of enzymatic demethylation of G-pectin on the activity of PAE, PG and PL (left) The effect of pretreatment of G-pectin with PL on the activity of PAE (right)... 

The A. niger preparation investigated in this study contains at least three different acetyl esterases, each with its own specificity. The activities of RGAE and FAE are comparable to those of similar enzymes isolated previously from A. aculeatus and a different A. niger preparation. PAE appears to be a new enzyme, with an activity specific towards one type of acetyl ester in the homogalacturonan chain of beet pectin. 

Wu, D., Onwulata, C., Ren, Z., Pae, M., Pang, H., and Meydani, S. (2009). Effect of dietary supplementation with a formulated nutrient mixture together with whey-based protein on immune response of young and old mice. /. Fed. Am. Soc. Exp. Biol. 23, 909.7. 

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