Catalytic Activities Of [GADV]-Peptides

Abstract

We have previously postulated a novel hypothesis for the origin of life, assuming that life on the earth originated from "[GADV]-protein world", not from the "RNA world" (see Ikehara's review, 2002). The [GADV]-protein world is constituted from peptides and proteins with random sequences of four amino acids (glycine [G], alanine [A], aspartic acid [D] and valine [V]), which accumulated by pseudo-replication of the [GADV]-proteins. To obtain evidence for the hypothesis, we produced [GADV]-peptides by repeated heat-drying of the amino acids for 30 cycles ([GADV]-P(30)) and examined whether the peptides have some catalytic activities or not. From the results, it was found that the [GADV]-P(30) can hydrolyze several kinds of chemical bonds in molecules, such as umbelliferyl-beta-D-galactoside, glycine-p-nitroanilide and bovine serum albumin. This suggests that [GADV]-P(30) could play an important role in the accumulation of [GADV]-proteins through pseudo-replication, leading to the emergence of life. We further show that [GADV]-octapaptides with random sequences, but containing no cyclic compounds as diketepiperazines, have catalytic activity, hydrolyzing peptide bonds in a natural protein, bovine serum albumin. The catalytic activity of the octapeptides was much higher than the [GADV]-P(30) produced through repeated heat-drying treatments. These results also support the [GADV]-protein-world hypothesis of the origin of life (see Ikehara's review, 2002). Possible steps for the emergence of life on the primitive earth are presented.

Catalysis in the Primordial World

“…37 Random synthesis of [GADV]-peptides by microwave heating produced a library of 1-4 kDa peptides, 38 which showed hydrolase-and oxidoreductase-like catalytic activities. 39 Against all odds of combinatorics, it is clear that catalytic peptides could have been easily formed on primordial Earth.…”

A History of Genomic Structures: The Big Picture

“…This hypothesis is known as the proteins (or peptides) fi rst hypothesis (Andras and Andras 2005 ). As shown by Oba et al ( 2005 ), peptides with catalytic activity could accumulate and participate in the multiplication of primeval proteins by pseudo-replication in a process of repeated drying-heating cycles; thus, without the need of an RNA-based translation system. Primeval proteins might have possessed the catalytic activity to promote the formation of cyanide and purines from amino acids (McGlynn et al 2010 ).…”

“…Ribozymelike molecules could have carried out the peptide synthesis of these primeval proteins. A GNC code (G for guanine, N for any of the four nucleotides, and C for cytosine) is suffi cient to encode the four amino acids Gly, Ala, aspartate (Asp), and valine (Val) able to form globular, water-soluble proteins with α-helix, β-sheet, and β-turn secondary structures (Ikehara 2009 ) that are capable of catalytic activities (Oba et al 2005 ). According to Ikehara ( 2009 ), this primitive code would have evolved fi rst to a code linking 16 codons and 10 amino acids, the so-called SNS (S for strong: G or C), and then the RNY (R for purines, Y for pyrimidines) ancestral codons (Carels and Frias 2013 ).…”

Cooperative induction of ordered peptide and fatty acid aggregates

“…Historically, the "origin of life" field has been polarized by competing, and seemingly exclusive hypotheses such as replication first (1), metabolism first (2) and compartmentalization first (3), or RNA world (4), peptide world (5,6) and amyloid world (7)(8)(9). It is evident that these hypotheses tend to oversimplify the problem and that at one point in the origin or evolution of early life, the primary molecules of biology, namely nucleic acids, amino acids, aliphatic compounds and sugars became intimately intertwined.…”