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


   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 


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 



Review By Sydney Edwards



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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