Biochemical study of Autism Spectrum Disorder patients : 9783659642579 : 03 Dec 2014 : Many hypotheses were supposed as autism spectrum disorder(ASD)causes. Dipeptidyl peptidase-4 deficiency and opioids compounds formation, oxidative stress and environmental toxicants exposure were studied. So many biochemical parameters as Melatonin (MEL), Neuroglobin(NGB),Antioxidant Activity(AOA), Advanced Oxidation Protein Products (AOPP), Thiobarbituric Acid Reactive Substances (TBARS), Nitric Oxide(No), Glutathione (GSH) were studied. Also, Dipeptidyl Peptidase-4(DPP-4), Glutathione-S-Transferase(GST), Acetyl Cholinesterase (AChE), Myeloperoxidase (MPO), Aryl Esterase, Xanthine Oxidase (XO)activities were estimated. Many techniques were used in this study such as HPLC, SDS-PAGE and gel filtration chromatography,protein precipitation,dialysis, molecular weight determination,estimation of total protein by modified Lowry and studying the optimum conditions of serum DPP-4. The future studies must inc