Research Progress of Pectin Methylesterase and its Inhibitors.

As an important pectin enzyme, pectin methylesterase (PME) can hydrolyze methyl esters, release methanol and reduce esterification. It is essential in regulating pollen tube development, root extension, and fruit ripening. Pectin methylesterase inhibitors (PMEI) can specifically bind PME and inhibit its activity, which jointly determines the esterification degree of pectin. PMEI has important application prospects in plant pest control, fruits and vegetable processing fields. In this paper, the gene families, crystal structures, molecular recognition, and applications in plants and industry are reviewed for the PME and PMEI systems. Finally, the semi-rational design of PMEI is discussed and discussed prospected.

[The influence of in awake and sleeping to the thresholds of ASSR].

OBJECTIVE: To explore the difference of the threshold of auditory steady-state evoked responses (ASSR) in awake and sleeping. METHOD: Fifteen adults (30 ears) with normal hearing were selected to ASSR test. ASSR parameters: carrier frequency (CM)are 0.5, 1.0, 2.0, 3.0, 4.0, 6.0 kHz, modulation frequency (FM) are 46.81 Hz. The test was performed in two different status (in awake and sleeping). RESULT: In awake, the thresholds of ASSR with FM of 46 Hz are significantly lower than 81 Hz (P < 0.01); In sleeping, the thresholds of ASSR with FM of 81 Hz are lower than 46 Hz above 2 kHz CM (P < 0.05), which thresholds were close to pure tone. CONCLUSION: To select low modulate (46 Hz) frequency in awake, and use high modulate (81 Hz) frequency in sleeping. When perform ASSR test, the test values are closer to the actual hearing threshold.

An Arabidopsis cell wall-associated kinase required for invertase activity and cell growth.

The wall-associated kinases (WAK), a family of five proteins that contain extracellular domains that can be linked to pectin molecules of the cell wall, span the plasma membrane and have a cytoplasmic serine/threonine kinase domain. Previous work has shown that a reduction in WAK protein levels leads to a loss of cell expansion, indicating that these receptor-like proteins have a role in cell shape formation. Here it is shown that a single wak2 mutation exhibits a dependence on sugars and salts for seedling growth. This mutation also reduces the expression and activity of vacuolar invertase, often a key factor in turgor and expansion. WAKs may thus provide a molecular mechanism linking cell wall sensing (via pectin attachment) to regulation of solute metabolism, which in turn is known to be involved in turgor maintenance in growing cells.