2. Biochemically important nucleotide bases, nucleosides, nucleotides and nucelotide derivatives. Structure and properties

what are the bases involved in DNA and RNA?

adenine

cytosine

guanine

thymine

uracil

how do nucleotides carry chemical energy in cells?

the phosphate group is covalently linked to the 5’OH-group at the ribonucleotide may have one or two additional phosphate bonds

they are ATP, GTP, UTP, CTP

they contain anhydride bonds which can release high amounts of energy when cleaved

adenosine as cofactor?

adenosine doesn’t directly participate in the function, but without it activity decreases

notable cofactors are: coenzyme A, NAD and FAD

CoA?

CoA is a enzyme consiting of adenosine and pantothenic acid and β-mercaptoethylamine

its function is in acyl group transfer enzymes

the acyl group is connected by a thioester bond between the β-mercaptoethylamine

NAD?

is a dinucleotide consisting of an adenine nucleotide and a nicotinamide connected by a phosphoanhydride bond

it exists in two forms NAD+/NADH

when it picks up an H+ ion, it is reduced and carries two electrons

often used in DH reactions

NAD and NADH absorbs UV-light

at 340 nm NADH has a maxima, while NAD+ doesn’t → this is known as warburgs optical test

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FAD?

consist of a adenine nucleotide and riboflavin

it is also an electron carrier

FAD can accept two hydrogens and 2e-

is important in flavoproteins such as PPC, ⍺-ketoglut DHC and succinate DH

unlike NAD, FAD can also accept only one H+ and one e-, it can be more versatile than NAD

NADP?

NADP is closely related to NAD in structure, the only difference is that NADPH has a phosphate group on the 2nd C of the adenine nucl.

while NADH is an important electron carrier for energy production, NADPH is more important in biosynthesis by reductase enzymes

In the cell NADPH is mostly found in cytoplasm (where anabolic reactions usually occur) while NADH is mostly in mitochondria

nucleotides as regulatory molecules?

cell responds to their environment by taking cues from hormones or other external signals

they are first messengers, and their interaction w. their receptor usually leads to formation of secondary messengers, often nucleotides

cAMP?

product of adenylyl cyclase

3’,5’-cyclic AMP is connected by the P of the 3C and the O-connected to the 5th C

cAMP activates PKA, this is a part of the glucagon/epinephrine signalling pathway

cGMP?

cGMP is produced by guanylyl cyclase

structurally similar to cAMP except the base is an guanosine

cGMP is an important molecule in visual pathway and activation of PKG