Can someone cogently describe the tyrosinase + condition?

I've been reading a little lately, and i just recently got my albino bloods so I'm more curious than ever. What does T+ albinism truly define? Why is it considered to be lacking black pigment when the pupils are visibly black? Obviously it truly does lack black coloration, but the pupils/retinas have me wondering. This is what I read at the Barker's website...

A t+ albino snake is able to create tyrosinase, and then can accomplish the first two steps of melanin synthesis. But a t+ albino is lacking a necessary enzyme for one of the subsequent steps. There is a different enzyme for each step, but which enzyme is defective is not specified

So is it true that we don't really know what T+ actually is? I would just like some kind of confirmation, or other opinions. The barkers identify that tyrosine eventually turns into dopaquinone after two steps which is just a "black compound" so is this why the T+ pupils are black, as opposed to that T- albino bunny I just saw, whose eyes and pupils were completely pink? Interesting stuff...
John

Originally Posted by CherryFive

I've been reading a little lately, and i just recently got my albino bloods so I'm more curious than ever. What does T+ albinism truly define? Why is it considered to be lacking black pigment when the pupils are visibly black? Obviously it truly does lack black coloration, but the pupils/retinas have me wondering. This is what I read at the Barker's website...

A t+ albino snake is able to create tyrosinase, and then can accomplish the first two steps of melanin synthesis. But a t+ albino is lacking a necessary enzyme for one of the subsequent steps. There is a different enzyme for each step, but which enzyme is defective is not specified

So is it true that we don't really know what T+ actually is? I would just like some kind of confirmation, or other opinions. The barkers identify that tyrosine eventually turns into dopaquinone after two steps which is just a "black compound" so is this why the T+ pupils are black, as opposed to that T- albino bunny I just saw, whose eyes and pupils were completely pink? Interesting stuff...
John

From a strictly genetic and biochemical point of view

The gene which results in albinism prevents the body from making the usual amounts of a pigment called melanin. Albinism is typically categorised as Tyrosinase positive or negative. In cases of Tyrosinase positive albinism, the enzyme tyrosinase is present but is unable to enter pigment cells to produce melanin. In tyrosinase negative cases, this enzyme is not produced.

That was taken from Wikpedia. Click on the link for the full article.

It is 100% true that we don't really know what T+ albino actually is.

T+ albinism is a mess. T- albinism is caused by a nonfunctional tyrosinase enzyme. H. B. (Bern) Bechtel tested several species and found some with T- albinism and some with T+ albinism. You might want to look at his book, Amphibian and Reptile Variants for details of the test. When he used the T+ albino term, he meant a snake that lacked melanin pigment, including in the eyes. But the T+ snake did not test out as having nonfunctional tyrosinase. The conclusion was it was an albino for some reason other than tyrosinase. But so far we have no clue as to the actual biochemical cause. And there are likely to be several causes for the condition.

Since Bechtel started using the term, herper useage has broadened it to the point where nearly any snake that is lighter than normal for genetic reasons has been called T+ albino. It has become such a catch-all term that it is practically meaningless.

Depending on which T+ albino you choose, the eyes could be as pink as a T- albino's eyes, or range through shades of red all the way to black.

As far as I know, dopaquinone is not a black compound. Dopaquinone has to go through several more chemical changes and a polymerization step before being deposited in a protein matrix which becomes the pigment granule, which is black or brown.

Hope this helps.

Paul H,
I want to publicly apologize for not responding sooner to this thread. I really dug everything you wrote there. It was a thoughtful and insightful read!
Perhaps the next question on my mind is, "how to biochemically determine what ensues T+ albinism". When looking at a Caramel Boa, a T+ ball python, and a T+ blood python, they seem to share a general characteristic that sight alone cannot describe. I guess they are just less black, but as you pointed out, could be for different reasons. Again, sorry for being so late in reading your neat post..!

Best,
John Wright

Glad the post was helpful. From the limited initial response and time lag before I posted, I wasn't surprised that there was no reply.

I don't know a lot about biochemistry. But in my opinion, before starting on the biochem, someone needs to look at the pigment cells under a microscope. Just determining whether the actual cells are abnormal or whether the intracellular pigment granules are abnormal in number, size, shape, or distribution would help.