The sequence of physiological reactions leading to dopamine is;

l-phenylalanine -> l-tyrosine -> l-DOPA -> dopamine.

Humans can't make l-phenylalanine, it has to be provided in the diet, however we can make l-tyrosine, although it is present in dietary protein.

If you eat food with adequate protein in it you get plenty of l-phenylalanine and l-tyrosine in your diet from the breakdown of the protein into its amino acids.

Healthy dopaminergic neurons can perform all three of these reactions provided there are adequate enzymes and co-factors. As I understand it, in PD the problem is the loss of healthy neurons, not a lack of either l-phenylalanine or l-tyrosine for dopamine production.

But I understand that L-dopa treatment implies that L-dopa is converted to dopamine by same sick neurons? If so why these cells fail to do the
l-phenylalanine -> l-tyrosine -> l-DOPA conversion?

Unfortunately, this product does not list the exact amounts of
amino acids on the label. They are all lumped together along with the undisclosed amount of caffeine, as a proprietary mixture.

We have a current thread on this product on PN with discussion.
It revolves around the fact that most of the ingredients are not listed in a useful manner.

So we do NOT know how much of the various aminos (except the B6) are in there.
one of our posters at PN found a website that did discover how much caffeine was in the regular red bottle.... 130 or so milligrams.

When products are secretive like this, it is impossible to know what is doing what etc.

http://neurotalk.psychcentral.com/thread165495.html

Imad,
As I understand, the remaining few healthy dopaminergic neurons can't keep up with the need for dopamine because the first and second reactions which produce tyrosine and DOPA are rate-limiting, or slower. However, as long as there are some neurons still functioning, they can convert exogenous l-DOPA to dopamine by that faster final reaction.

OK, so why does it take so much longer for our ldopa (sinemet) to take effect than it does the 5-hour drink? And I mean, it' s a huge difference! With that analysis, it should actually take longer for the drink to have an effect, since those sick dopamine neurons are having to go through three conversions (LP-tyrosine-ldopa-dopamine) instead of just one (ldopa-dopamine).

We are wondering if we might shouldn't instead be looking at the drink's impact on epinephrine as the causative factor for us...