Question

lser Glyceraldehyde 3-phosphate NAD CONH2 H -N + HH Hemithioacetal Oxidation NAD NADH CONH CONH2 Но RN + H -N / H Η Η Hн s NADH NAD Thioester intermediate Thioester intermediate Phosphorylation CONH2 O R N + -H 2-O,PO FIGURE 16.8 Catalytic mechanism of glyceraldehyde 3-phosphate dehydrogenase. The reaction proceeds through a thioester intermediate, which allows the oxidation of glyceraldehyde to be coupled to the phosphorylation of 3-phosphoglycerate. (1) Cysteine reacts with the aldehyde group of the substrate, forming a hemithioacetal. (2) An oxidation takes place with the transfer of a hydride ion to NAD", forming a thioester. This reaction is facilitated by the transfer of a proton to histidine. (3) The reduced NADH is exchanged for an NAD+ molecule. (4) Orthophosphate attacks the thioester, forming the product 1,3-BPG. su 1,3-BPG HHSH

The mechanism of glyceraldehyde 3 phosphate dehydrogenase. In step 1 (Top Left) the sulfur from the cysteine loses its hydrogen to the carbonyl carbon of the substrate. I think is wrong and the hydrogen is stolen by the histidine (nitrogen) using a base catalyst reaction.

Answer 1

Yes, you are right it is abstracted by Histidine but in this note book it is abstracted in second step. The correct mechanism is :

NAD NADH Cy Glyceraldehyde-3- phosphate HCO -5 / HH-C-OH CHOPO, HO C- Cyr- NH H-C-OH CH,OPO, HC-OM CH,OPO, OPO, Cyle -OH WHC-OH sản CH,OPO - H-C-OH CH,OPO, 1,3-Bisphospho- glycerate Scanned with CamScanner