Do acetyl-CoA, acetyl-CoA carboxylase and acetyl-glutamate carry any charge?

Question

Do the following compounds have any charge? If not, then why? If yes, is there any database that would give me this information if the compound is negatively or positively charged?

The compounds are as follows:

Acetyl-CoA
Acetyl-CoA carboxylase
Acetyl-glutamate

I have searched and somehow I am getting more confused.

Answer 1

chemicalize.org is a good utility for predicting many molecular properties such as pKa, pI and charge. The Human Metabolome Database uses the same underlying software but tabulates some of the data (eg charge is explicitly stated).

Acetyl-CoA, for example, has a pI of 1.32 and charge of -4 at pH=7.4.

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Your second link is to a portion of an enzyme (a serine residue that gets phosphorylated). Prediction of protein properties can be done with ProtParam.

Human Acetyl-CoA Carboxylase 1, for example, has a pI of 5.95 and charge of -39.

Answer 2

The first compound you mention is acetyl-co-enzyme A (acetyl-CoA) (first picture, left panel). The acetyl group is uncharged, but the co-enzyme A (CoA) group (Fig. 1, right panel) does carry charge through its phosphate groups. In normal physiologic environments these phosphate groups will donate one or more protons, leaving the molecule negatively charged, as shown in Fig. 1, right panel below:

^{Fig. 1 Acetyl-CoA (left) and the co-enzyme A group (right).}

The second compound is an enzyme, namely acetyl-CoA carboxylase. Consisting of many, many amino-acids it will carry many, many charges under physiological conditions. Some of these will be negative, some positive.

The third compound you mention is acetyl-glutamate:

^{Acetyl-Glutamate}

This compound carries two carboxyl groups, which makes the compound acidic and negatively charged under physiological conditions, as it will donate one or two protons to the environment, dependent on the pH.

^{PS: For an in-depth answer on the basic chemistry and pKa values I would ask this at Chemistry.SE :)}