Chemistry Review 1: Nitric Oxide Activates β-Cell Glucokinase by Promoting Formation of the “Glucose-Activated” State


Chemistry Review 1:  Nitric Oxide Activates β-Cell Glucokinase by Promoting Formation of     
                                                        the “Glucose Activated” State



For my first chemistry review article for the blog I decided to 



summarize an article in the field of biochemistry. My goal is to 




provide readers with a wide range of subtopics within this field; 



as well as, environmental science and technology. To provide a 




little background about myself, I have a bachelor of 



science in Chemistry with a concentration in Chemistry 




professional. concentration in Chemistry professional means that 



took a heavy college-course load of chemistry and math classes. 




This extensive list of courses qualifies mto work in a research 





lab. I have worked two years in an analytical lab. My 




current position is a laboratory technician for a chemical 




processing plant. I am also a member of the American Chemical 




Society (ACS); which is where all the journal articles I am plan to 




review can be found.For this week’s review, I have 





selected Nitric Oxide Activates β-Cell Glucokinase by Promoting 




Formation of the 
“Glucose-Activated” State. This article was 



selected because I used to be diabetic. As a teenager, I happened 





to be insulin resistant.  However, I lost weight and exercised; 




allowed me to get off my medication. The medication I was on was 




metformin. This specific drug has been used to treat type 2 diabetes 




by decreasing liver cells glucose production; this decrease results 




in decreasing intestinal uptake of glucose. My currently article is 




discussing the research of an active site on glucokinase (GCK). This 



is pertinent because when the pancreas releases insulin, the insulin 




hormone is highly regulated by GCK.








   So you may be wondering, “What does this have to do with people 



being diabetic?” Changes in blood sugar are due to the GCK activity 




which is coupled with Beta Cells (β-cell) metabolism. Beta cells 




are specialized cells within the pancreas that secrete insulin to 




regulate blood glucose concentrations. The researchers performed a 




study on low and high activity levels of GCK induction by three 





different methods. They performed these three different approach 




techniques because there have been previous studies that have 




showed different protein conformations (arrangements) for GCK. 




Studies have shown that there are different levels of enzymatic 



activity for GCK based on these different protein arrangements. 





Even with this previous studies findings, it remains unclear how 




living cells regulate GCK cooperativity. GCK cooperativity is when 




an enzyme has multiple binding sites where molecules can bind to 





positively stimulate a response within the cell.










 For better understanding of the process of GCK activation in living 




cells, as well as to determine how GCK is regulated, scientists 




have developed an approach called homotransfer to be able to trace 




and record what is occurring during GCK activation and activity. 




The homotransfer approach is using Förster resonance 




energy transfer (FRET). FRET allows scientists to analyze the 



individual GCK molecular arrangement.











  The authors used polarization microscopy to eliminate fluorescence 




crosstalk to improved the signal-to-noise ratio. Fluorescence 





crosstalk occurs when you have two biological makers, attached to a 




microscopic fluorescent materials,which are excited simultaneously. 




This simultaneous biomarker excitement produces an overlap between 




the two biomarkers' fluorescence resonation. This overlapped 





fluorescence resonation is scanned from the sample by the 





microscope:computer combination. Signal-to-noise ratio is when your 





sample has background noise all the time. An example of background 






noise produced occurs while the computer:microscope runs. The goal 





is to get signal-to-noise ratio as low as possible.

















   When studying GCK low activity levels, compared to high activity 




levels, the authors tested GCK activity with nitric oxide. Nitric 





Oxide (NO) is known to be GCK activators (GCA). Another known GCA 





is high glucose concentrations (+high glc).  The authors used FRET 




as a sensor technique after an incubation period had been 





concluded, and sample images were collected by fluorescence





microscopy. 










   Using fluorescent microscopy, the scientists were able to see the 





emissions illuminated on the sample with polarized light. They then 




collected fluorescent emissions in parallel and perpendicular 





directions. These directions are the two 





ways that the sample is scanned to collect the fluorescent 





emissions from the sample.The overall fluorescent ratio was 




calculated, and it was determined that nitric 




oxide facilitates the 




GCK transition into an 


active state. The 





active state 




of this enzyme is when 




it has a glucose 




molecule 




attached at the active site.










 Overall the study found that FRET GCK biosensor, and generally GCK-





FP fusions, to be useful as probes. This means that these probes 





help to be able to see the fluorescent emissions which could then 




been read by the instrument. Ultimately, this article has provided 





additional insight into understanding GCK regulations within living 




cells. The images of the fluorescent microscopy data within 




this article allowed scientists to rationalize that there are 




likely two shape states of GCK; based on GCK FRET data. This data 




lead scientists to conclude that there was two measurable GCK 




conformations within living cells.








   Additionally, this article found that the efficiency of FRET is 




greatly dependent on the distance separating the GKC (acceptor) and 




glucose (donor). If the overall distance is changed by 1 nanometer 



between the FRET pair can reduce the efficiency greatly. It also 



deserves mention that the authors did not observe significant 




differences, using FRET data, between the low-glucose and 



glucose-free conditions.








   The human body is a well-oiled machine, but every now and then 



there are discrepancies within the system. Often 




these discrepancies tie into the fields of biochemistry. Biochemist 




break down proteins, analyze, and sequence them. This article 




provides great insight into how the conformations GCK takes on 




within a living cell. This can potentially aid our overall 




understanding in diabetic disease states.









   Until next time, thank you for taking the time to learn about GCK 


with us at Evolution Through the Ages. Until next time, I am Sydney 


Edwards.







--------------------------------------------------------------------------------------------------------------------------

Reviewed By Sydney Edwards







--------------------------------------------------------------------------------------------------------------------------







Reference:






Kendra M. Seckinger, Vishnu P. Rao, Nicole E. Snell, Allison E. Mancini, Michele L. Markwardt, and M. A. Rizzo



Biochemistry 2018 57 (34), 5136-5144



DOI: 10.1021/acs.biochem.8b00333

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