Which of the following correctly explains the relationship between xanthine dehydrogenase (XDH)and xanthine oxidase (XO)?
A)in healthy tissue,XDH is abundant while XO is rarely found B)conversion of XDH to XO occurs under conditions that damage cells C)XDH is converted to XO by formation of a disulfide bond D)XDH is converted to XO by proteolysis E)all of the above
Which of the following correctly describes the activity or regulation of E coli ribonucleotide reductase?
A)the overall activity of the enzyme is controlled by ATP and dATP B)the specificity of the enzyme is controlled by all four dNTPs C)a tyrosine free radical participates in the reaction D)the reduction is not a result of simple hydride transfer E)all of the above